src/time64.c - third_party/libplist - Git at Google

 /*

 Copyright (c) 2007-2010  Michael G Schwern

 This software originally derived from Paul Sheer's pivotal_gmtime_r.c.

 The MIT License:

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.

 */

 /*

 Programmers who have available to them 64-bit time values as a 'long
 long' type can use localtime64_r() and gmtime64_r() which correctly
 converts the time even on 32-bit systems. Whether you have 64-bit time
 values will depend on the operating system.

 localtime64_r() is a 64-bit equivalent of localtime_r().

 gmtime64_r() is a 64-bit equivalent of gmtime_r().

 */

 #include <assert.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <time.h>
 #include <errno.h>
 #include "time64.h"
 #include "time64_limits.h"


 static const char days_in_month[2][12] = {
     {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
     {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
 };

 static const short julian_days_by_month[2][12] = {
     {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334},
     {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335},
 };

 static const char wday_name[7][4] = {
     "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
 };

 static const char mon_name[12][4] = {
     "Jan", "Feb", "Mar", "Apr", "May", "Jun",
     "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
 };

 static const short length_of_year[2] = { 365, 366 };

 /* Some numbers relating to the gregorian cycle */
 static const Year     years_in_gregorian_cycle   = 400;
 #define               days_in_gregorian_cycle      ((365 * 400) + 100 - 4 + 1)
 static const Time64_T seconds_in_gregorian_cycle = days_in_gregorian_cycle * 60LL * 60LL * 24LL;

 /* Year range we can trust the time funcitons with */
 #define MAX_SAFE_YEAR 2037
 #define MIN_SAFE_YEAR 1971

 /* 28 year Julian calendar cycle */
 #define SOLAR_CYCLE_LENGTH 28

 /* Year cycle from MAX_SAFE_YEAR down. */
 static const short safe_years_high[SOLAR_CYCLE_LENGTH] = {
     2016, 2017, 2018, 2019,
     2020, 2021, 2022, 2023,
     2024, 2025, 2026, 2027,
     2028, 2029, 2030, 2031,
     2032, 2033, 2034, 2035,
     2036, 2037, 2010, 2011,
     2012, 2013, 2014, 2015
 };

 /* Year cycle from MIN_SAFE_YEAR up */
 static const int safe_years_low[SOLAR_CYCLE_LENGTH] = {
     1996, 1997, 1998, 1971,
     1972, 1973, 1974, 1975,
     1976, 1977, 1978, 1979,
     1980, 1981, 1982, 1983,
     1984, 1985, 1986, 1987,
     1988, 1989, 1990, 1991,
     1992, 1993, 1994, 1995,
 };

 /* This isn't used, but it's handy to look at */
 #if 0
 static const char dow_year_start[SOLAR_CYCLE_LENGTH] = {
     5, 0, 1, 2,     /* 0       2016 - 2019 */
     3, 5, 6, 0,     /* 4  */
     1, 3, 4, 5,     /* 8       1996 - 1998, 1971*/
     6, 1, 2, 3,     /* 12      1972 - 1975 */
     4, 6, 0, 1,     /* 16 */
     2, 4, 5, 6,     /* 20      2036, 2037, 2010, 2011 */
     0, 2, 3, 4      /* 24      2012, 2013, 2014, 2015 */
 };
 #endif

 /* Let's assume people are going to be looking for dates in the future.
    Let's provide some cheats so you can skip ahead.
    This has a 4x speed boost when near 2008.
 */
 /* Number of days since epoch on Jan 1st, 2008 GMT */
 #define CHEAT_DAYS  (1199145600 / 24 / 60 / 60)
 #define CHEAT_YEARS 108

 #define IS_LEAP(n)      ((!(((n) + 1900) % 400) || (!(((n) + 1900) % 4) && (((n) + 1900) % 100))) != 0)
 #define WRAP(a,b,m)     ((a) = ((a) <  0  ) ? ((b)--, (a) + (m)) : (a))

 #ifdef USE_SYSTEM_LOCALTIME
 #    define SHOULD_USE_SYSTEM_LOCALTIME(a)  (       \
     (a) <= SYSTEM_LOCALTIME_MAX &&              \
     (a) >= SYSTEM_LOCALTIME_MIN                 \
 )
 #else
 #    define SHOULD_USE_SYSTEM_LOCALTIME(a)      (0)
 #endif

 #ifdef USE_SYSTEM_GMTIME
 #    define SHOULD_USE_SYSTEM_GMTIME(a)     (       \
     (a) <= SYSTEM_GMTIME_MAX    &&              \
     (a) >= SYSTEM_GMTIME_MIN                    \
 )
 #else
 #    define SHOULD_USE_SYSTEM_GMTIME(a)         (0)
 #endif

 /* Multi varadic macros are a C99 thing, alas */
 #ifdef TIME_64_DEBUG
 #    define TIME64_TRACE(format) (fprintf(stderr, format))
 #    define TIME64_TRACE1(format, var1)    (fprintf(stderr, format, var1))
 #    define TIME64_TRACE2(format, var1, var2)    (fprintf(stderr, format, var1, var2))
 #    define TIME64_TRACE3(format, var1, var2, var3)    (fprintf(stderr, format, var1, var2, var3))
 #else
 #    define TIME64_TRACE(format) ((void)0)
 #    define TIME64_TRACE1(format, var1) ((void)0)
 #    define TIME64_TRACE2(format, var1, var2) ((void)0)
 #    define TIME64_TRACE3(format, var1, var2, var3) ((void)0)
 #endif


 static int is_exception_century(Year year)
 {
     int is_exception = ((year % 100 == 0) && !(year % 400 == 0));
     TIME64_TRACE1("# is_exception_century: %s\n", is_exception ? "yes" : "no");

     return(is_exception);
 }


 /* Compare two dates.
    The result is like cmp.
    Ignores things like gmtoffset and dst
 */
 static int cmp_date( const struct TM* left, const struct tm* right ) {
     if( left->tm_year > right->tm_year )
         return 1;
     if( left->tm_year < right->tm_year )
         return -1;
     if( left->tm_mon > right->tm_mon )
         return 1;
     if( left->tm_mon < right->tm_mon )
         return -1;
     if( left->tm_mday > right->tm_mday )
         return 1;
     if( left->tm_mday < right->tm_mday )
         return -1;
     if( left->tm_hour > right->tm_hour )
         return 1;
     if( left->tm_hour < right->tm_hour )
         return -1;
     if( left->tm_min > right->tm_min )
         return 1;
     if( left->tm_min < right->tm_min )
         return -1;
     if( left->tm_sec > right->tm_sec )
         return 1;
     if( left->tm_sec < right->tm_sec )
         return -1;
     return 0;
 }


 /* Check if a date is safely inside a range.
    The intention is to check if its a few days inside.
 */
 static int date_in_safe_range( const struct TM* date, const struct tm* min, const struct tm* max ) {
     if( cmp_date(date, min) == -1 )
         return 0;

     if( cmp_date(date, max) == 1 )
         return 0;

     return 1;
 }


 /* timegm() is not in the C or POSIX spec, but it is such a useful
    extension I would be remiss in leaving it out.  Also I need it
    for localtime64()
 */
 Time64_T timegm64(const struct TM *date) {
     Time64_T days    = 0;
     Time64_T seconds = 0;
     Year     year;
     Year     orig_year = (Year)date->tm_year;
     int      cycles  = 0;

     if( (orig_year > 100) || (orig_year < -300) ) {
         cycles = (orig_year - 100) / 400;
         orig_year -= cycles * 400;
         days      += (Time64_T)cycles * days_in_gregorian_cycle;
     }
     TIME64_TRACE3("# timegm/ cycles: %d, days: %lld, orig_year: %lld\n", cycles, days, orig_year);

     if( orig_year > 70 ) {
         year = 70;
         while( year < orig_year ) {
             days += length_of_year[IS_LEAP(year)];
             year++;
         }
     }
     else if ( orig_year < 70 ) {
         year = 69;
         do {
             days -= length_of_year[IS_LEAP(year)];
             year--;
         } while( year >= orig_year );
     }

     days += julian_days_by_month[IS_LEAP(orig_year)][date->tm_mon];
     days += date->tm_mday - 1;

     seconds = days * 60 * 60 * 24;

     seconds += date->tm_hour * 60 * 60;
     seconds += date->tm_min * 60;
     seconds += date->tm_sec;

     return(seconds);
 }


 static int check_tm(struct TM *tm)
 {
     /* Don't forget leap seconds */
     assert(tm->tm_sec >= 0);
     assert(tm->tm_sec <= 61);

     assert(tm->tm_min >= 0);
     assert(tm->tm_min <= 59);

     assert(tm->tm_hour >= 0);
     assert(tm->tm_hour <= 23);

     assert(tm->tm_mday >= 1);
     assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]);

     assert(tm->tm_mon  >= 0);
     assert(tm->tm_mon  <= 11);

     assert(tm->tm_wday >= 0);
     assert(tm->tm_wday <= 6);

     assert(tm->tm_yday >= 0);
     assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]);

 #ifdef HAVE_TM_TM_GMTOFF
     assert(tm->tm_gmtoff >= -24 * 60 * 60);
     assert(tm->tm_gmtoff <=  24 * 60 * 60);
 #endif

     return 1;
 }


 /* The exceptional centuries without leap years cause the cycle to
    shift by 16
 */
 static Year cycle_offset(Year year)
 {
     const Year start_year = 2000;
     Year year_diff  = year - start_year;
     Year exceptions;

     if( year > start_year )
         year_diff--;

     exceptions  = year_diff / 100;
     exceptions -= year_diff / 400;

     TIME64_TRACE3("# year: %lld, exceptions: %lld, year_diff: %lld\n",
           year, exceptions, year_diff);

     return exceptions * 16;
 }

 /* For a given year after 2038, pick the latest possible matching
    year in the 28 year calendar cycle.

    A matching year...
    1) Starts on the same day of the week.
    2) Has the same leap year status.

    This is so the calendars match up.

    Also the previous year must match.  When doing Jan 1st you might
    wind up on Dec 31st the previous year when doing a -UTC time zone.

    Finally, the next year must have the same start day of week.  This
    is for Dec 31st with a +UTC time zone.
    It doesn't need the same leap year status since we only care about
    January 1st.
 */
 static int safe_year(const Year year)
 {
     int _safe_year = (int)year;
     Year year_cycle;

     if( year >= MIN_SAFE_YEAR && year <= MAX_SAFE_YEAR ) {
         return _safe_year;
     }

     year_cycle = year + cycle_offset(year);

     /* safe_years_low is off from safe_years_high by 8 years */
     if( year < MIN_SAFE_YEAR )
         year_cycle -= 8;

     /* Change non-leap xx00 years to an equivalent */
     if( is_exception_century(year) )
         year_cycle += 11;

     /* Also xx01 years, since the previous year will be wrong */
     if( is_exception_century(year - 1) )
         year_cycle += 17;

     year_cycle %= SOLAR_CYCLE_LENGTH;
     if( year_cycle < 0 )
         year_cycle = SOLAR_CYCLE_LENGTH + year_cycle;

     assert( year_cycle >= 0 );
     assert( year_cycle < SOLAR_CYCLE_LENGTH );
     if( year < MIN_SAFE_YEAR )
         _safe_year = safe_years_low[year_cycle];
     else if( year > MAX_SAFE_YEAR )
         _safe_year = safe_years_high[year_cycle];
     else
         assert(0);

     TIME64_TRACE3("# year: %lld, year_cycle: %lld, safe_year: %d\n",
           year, year_cycle, _safe_year);

     assert(_safe_year <= MAX_SAFE_YEAR && _safe_year >= MIN_SAFE_YEAR);

     return _safe_year;
 }


 void copy_tm_to_TM64(const struct tm *src, struct TM *dest) {
     if( src == NULL ) {
         memset(dest, 0, sizeof(*dest));
     }
     else {
 #       ifdef USE_TM64
             dest->tm_sec        = src->tm_sec;
             dest->tm_min        = src->tm_min;
             dest->tm_hour       = src->tm_hour;
             dest->tm_mday       = src->tm_mday;
             dest->tm_mon        = src->tm_mon;
             dest->tm_year       = (Year)src->tm_year;
             dest->tm_wday       = src->tm_wday;
             dest->tm_yday       = src->tm_yday;
             dest->tm_isdst      = src->tm_isdst;

 #           ifdef HAVE_TM_TM_GMTOFF
                 dest->tm_gmtoff  = src->tm_gmtoff;
 #           endif

 #           ifdef HAVE_TM_TM_ZONE
                 dest->tm_zone  = src->tm_zone;
 #           endif

 #       else
             /* They're the same type */
             memcpy(dest, src, sizeof(*dest));
 #       endif
     }
 }


 void copy_TM64_to_tm(const struct TM *src, struct tm *dest) {
     if( src == NULL ) {
         memset(dest, 0, sizeof(*dest));
     }
     else {
 #       ifdef USE_TM64
             dest->tm_sec        = src->tm_sec;
             dest->tm_min        = src->tm_min;
             dest->tm_hour       = src->tm_hour;
             dest->tm_mday       = src->tm_mday;
             dest->tm_mon        = src->tm_mon;
             dest->tm_year       = (int)src->tm_year;
             dest->tm_wday       = src->tm_wday;
             dest->tm_yday       = src->tm_yday;
             dest->tm_isdst      = src->tm_isdst;

 #           ifdef HAVE_TM_TM_GMTOFF
                 dest->tm_gmtoff  = src->tm_gmtoff;
 #           endif

 #           ifdef HAVE_TM_TM_ZONE
                 dest->tm_zone  = src->tm_zone;
 #           endif

 #       else
             /* They're the same type */
             memcpy(dest, src, sizeof(*dest));
 #       endif
     }
 }


 #ifndef HAVE_LOCALTIME_R
 /* Simulate localtime_r() to the best of our ability */
 static struct tm * fake_localtime_r(const time_t *time, struct tm *result) {
     const struct tm *static_result = localtime(time);

     assert(result != NULL);

     if( static_result == NULL ) {
         memset(result, 0, sizeof(*result));
         return NULL;
     }
     else {
         memcpy(result, static_result, sizeof(*result));
         return result;
     }
 }
 #endif


 #ifndef HAVE_GMTIME_R
 /* Simulate gmtime_r() to the best of our ability */
 static struct tm * fake_gmtime_r(const time_t *time, struct tm *result) {
     const struct tm *static_result = gmtime(time);

     assert(result != NULL);

     if( static_result == NULL ) {
         memset(result, 0, sizeof(*result));
         return NULL;
     }
     else {
         memcpy(result, static_result, sizeof(*result));
         return result;
     }
 }
 #endif


 static Time64_T seconds_between_years(Year left_year, Year right_year) {
     int increment = (left_year > right_year) ? 1 : -1;
     Time64_T seconds = 0;
     int cycles;

     if( left_year > 2400 ) {
         cycles = (left_year - 2400) / 400;
         left_year -= cycles * 400;
         seconds   += cycles * seconds_in_gregorian_cycle;
     }
     else if( left_year < 1600 ) {
         cycles = (left_year - 1600) / 400;
         left_year += cycles * 400;
         seconds   += cycles * seconds_in_gregorian_cycle;
     }

     while( left_year != right_year ) {
         seconds += length_of_year[IS_LEAP(right_year - 1900)] * 60 * 60 * 24;
         right_year += increment;
     }

     return seconds * increment;
 }


 Time64_T mktime64(struct TM *input_date) {
     struct tm safe_date;
     struct TM date;
     Time64_T  timev;
     Year      year = input_date->tm_year + 1900;

     if( date_in_safe_range(input_date, &SYSTEM_MKTIME_MIN, &SYSTEM_MKTIME_MAX) )
     {
         copy_TM64_to_tm(input_date, &safe_date);
         timev = (Time64_T)mktime(&safe_date);

         /* Correct the possibly out of bound input date */
         copy_tm_to_TM64(&safe_date, input_date);
         return timev;
     }

     /* Have to make the year safe in date else it won't fit in safe_date */
     date = *input_date;
     date.tm_year = safe_year(year) - 1900;
     copy_TM64_to_tm(&date, &safe_date);

     timev = (Time64_T)mktime(&safe_date);

     /* Correct the user's possibly out of bound input date */
     copy_tm_to_TM64(&safe_date, input_date);

     timev += seconds_between_years(year, (Year)(safe_date.tm_year) + 1900);

     return timev;
 }


 /* Because I think mktime() is a crappy name */
 Time64_T timelocal64(struct TM *date) {
     return mktime64(date);
 }


 struct TM *gmtime64_r (const Time64_T *in_time, struct TM *p)
 {
     int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday;
     Time64_T v_tm_tday;
     int leap;
     Time64_T m;
     Time64_T timev = *in_time;
     Year year = 70;
     int cycles = 0;

     assert(p != NULL);

     /* Use the system gmtime() if time_t is small enough */
     if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) {
         time_t safe_time = (time_t)*in_time;
         struct tm safe_date;
         GMTIME_R(&safe_time, &safe_date);

         copy_tm_to_TM64(&safe_date, p);
         assert(check_tm(p));

         return p;
     }

 #ifdef HAVE_TM_TM_GMTOFF
     p->tm_gmtoff = 0;
 #endif
     p->tm_isdst  = 0;

 #ifdef HAVE_TM_TM_ZONE
     p->tm_zone   = (char*)"UTC";
 #endif

     v_tm_sec =  (int)(timev % 60);
     timev /= 60;
     v_tm_min =  (int)(timev % 60);
     timev /= 60;
     v_tm_hour = (int)(timev % 24);
     timev /= 24;
     v_tm_tday = timev;

     WRAP (v_tm_sec, v_tm_min, 60);
     WRAP (v_tm_min, v_tm_hour, 60);
     WRAP (v_tm_hour, v_tm_tday, 24);

     v_tm_wday = (int)((v_tm_tday + 4) % 7);
     if (v_tm_wday < 0)
         v_tm_wday += 7;
     m = v_tm_tday;

     if (m >= CHEAT_DAYS) {
         year = CHEAT_YEARS;
         m -= CHEAT_DAYS;
     }

     if (m >= 0) {
         /* Gregorian cycles, this is huge optimization for distant times */
         cycles = (int)(m / (Time64_T) days_in_gregorian_cycle);
         if( cycles ) {
             m -= (cycles * (Time64_T) days_in_gregorian_cycle);
             year += (cycles * years_in_gregorian_cycle);
         }

         /* Years */
         leap = IS_LEAP (year);
         while (m >= (Time64_T) length_of_year[leap]) {
             m -= (Time64_T) length_of_year[leap];
             year++;
             leap = IS_LEAP (year);
         }

         /* Months */
         v_tm_mon = 0;
         while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) {
             m -= (Time64_T) days_in_month[leap][v_tm_mon];
             v_tm_mon++;
         }
     } else {
         year--;

         /* Gregorian cycles */
         cycles = (int)((m / (Time64_T) days_in_gregorian_cycle) + 1);
         if( cycles ) {
             m -= (cycles * (Time64_T) days_in_gregorian_cycle);
             year += (cycles * years_in_gregorian_cycle);
         }

         /* Years */
         leap = IS_LEAP (year);
         while (m < (Time64_T) -length_of_year[leap]) {
             m += (Time64_T) length_of_year[leap];
             year--;
             leap = IS_LEAP (year);
         }

         /* Months */
         v_tm_mon = 11;
         while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) {
             m += (Time64_T) days_in_month[leap][v_tm_mon];
             v_tm_mon--;
         }
         m += (Time64_T) days_in_month[leap][v_tm_mon];
     }

     p->tm_year = year;
     if( p->tm_year != year ) {
 #ifdef EOVERFLOW
         errno = EOVERFLOW;
 #endif
         return NULL;
     }

     /* At this point m is less than a year so casting to an int is safe */
     p->tm_mday = (int) m + 1;
     p->tm_yday = julian_days_by_month[leap][v_tm_mon] + (int)m;
     p->tm_sec  = v_tm_sec;
     p->tm_min  = v_tm_min;
     p->tm_hour = v_tm_hour;
     p->tm_mon  = v_tm_mon;
     p->tm_wday = v_tm_wday;

     assert(check_tm(p));

     return p;
 }


 struct TM *localtime64_r (const Time64_T *timev, struct TM *local_tm)
 {
     time_t safe_time;
     struct tm safe_date;
     struct TM gm_tm;
     Year orig_year;
     int month_diff;

     assert(local_tm != NULL);

     /* Use the system localtime() if time_t is small enough */
     if( SHOULD_USE_SYSTEM_LOCALTIME(*timev) ) {
         safe_time = (time_t)*timev;

         TIME64_TRACE1("Using system localtime for %lld\n", *timev);

         LOCALTIME_R(&safe_time, &safe_date);

         copy_tm_to_TM64(&safe_date, local_tm);
         assert(check_tm(local_tm));

         return local_tm;
     }

     if( gmtime64_r(timev, &gm_tm) == NULL ) {
         TIME64_TRACE1("gmtime64_r returned null for %lld\n", *timev);
         return NULL;
     }

     orig_year = gm_tm.tm_year;

     if (gm_tm.tm_year > (2037 - 1900) ||
         gm_tm.tm_year < (1970 - 1900)
        )
     {
         TIME64_TRACE1("Mapping tm_year %lld to safe_year\n", (Year)gm_tm.tm_year);
         gm_tm.tm_year = safe_year((Year)(gm_tm.tm_year) + 1900) - 1900;
     }

     safe_time = (time_t)timegm64(&gm_tm);
     if( LOCALTIME_R(&safe_time, &safe_date) == NULL ) {
         TIME64_TRACE1("localtime_r(%d) returned NULL\n", (int)safe_time);
         return NULL;
     }

     copy_tm_to_TM64(&safe_date, local_tm);

     local_tm->tm_year = orig_year;
     if( local_tm->tm_year != orig_year ) {
         TIME64_TRACE2("tm_year overflow: tm_year %lld, orig_year %lld\n",
               (Year)local_tm->tm_year, (Year)orig_year);

 #ifdef EOVERFLOW
         errno = EOVERFLOW;
 #endif
         return NULL;
     }


     month_diff = local_tm->tm_mon - gm_tm.tm_mon;

     /*  When localtime is Dec 31st previous year and
         gmtime is Jan 1st next year.
     */
     if( month_diff == 11 ) {
         local_tm->tm_year--;
     }

     /*  When localtime is Jan 1st, next year and
         gmtime is Dec 31st, previous year.
     */
     if( month_diff == -11 ) {
         local_tm->tm_year++;
     }

     /* GMT is Jan 1st, xx01 year, but localtime is still Dec 31st
        in a non-leap xx00.  There is one point in the cycle
        we can't account for which the safe xx00 year is a leap
        year.  So we need to correct for Dec 31st comming out as
        the 366th day of the year.
     */
     if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 )
         local_tm->tm_yday--;

     assert(check_tm(local_tm));

     return local_tm;
 }


 static int valid_tm_wday( const struct TM* date ) {
     if( 0 <= date->tm_wday && date->tm_wday <= 6 )
         return 1;

     return 0;
 }

 static int valid_tm_mon( const struct TM* date ) {
     if( 0 <= date->tm_mon && date->tm_mon <= 11 )
         return 1;

     return 0;
 }


 char *asctime64_r( const struct TM* date, char *result ) {
     /* I figure everything else can be displayed, even hour 25, but if
        these are out of range we walk off the name arrays */
     if( !valid_tm_wday(date) || !valid_tm_mon(date) )
         return NULL;

     sprintf(result, TM64_ASCTIME_FORMAT,
         wday_name[date->tm_wday],
         mon_name[date->tm_mon],
         date->tm_mday, date->tm_hour,
         date->tm_min, date->tm_sec,
         1900 + date->tm_year);

     return result;
 }


 char *ctime64_r( const Time64_T* timev, char* result ) {
     struct TM date;

     if (!localtime64_r( timev, &date ))
         return NULL;

     return asctime64_r( &date, result );
 }
	/*

	Copyright (c) 2007-2010 Michael G Schwern

	This software originally derived from Paul Sheer's pivotal_gmtime_r.c.

	The MIT License:

	Permission is hereby granted, free of charge, to any person obtaining a copy
	of this software and associated documentation files (the "Software"), to deal
	in the Software without restriction, including without limitation the rights
	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	copies of the Software, and to permit persons to whom the Software is
	furnished to do so, subject to the following conditions:

	The above copyright notice and this permission notice shall be included in
	all copies or substantial portions of the Software.

	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	THE SOFTWARE.

	*/

	/*

	Programmers who have available to them 64-bit time values as a 'long
	long' type can use localtime64_r() and gmtime64_r() which correctly
	converts the time even on 32-bit systems. Whether you have 64-bit time
	values will depend on the operating system.

	localtime64_r() is a 64-bit equivalent of localtime_r().

	gmtime64_r() is a 64-bit equivalent of gmtime_r().

	*/

	#include <assert.h>
	#include <stdlib.h>
	#include <stdio.h>
	#include <string.h>
	#include <time.h>
	#include <errno.h>
	#include "time64.h"
	#include "time64_limits.h"


	static const char days_in_month[2][12] = {
	{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
	{31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
	};

	static const short julian_days_by_month[2][12] = {
	{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334},
	{0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335},
	};

	static const char wday_name[7][4] = {
	"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
	};

	static const char mon_name[12][4] = {
	"Jan", "Feb", "Mar", "Apr", "May", "Jun",
	"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
	};

	static const short length_of_year[2] = { 365, 366 };

	/* Some numbers relating to the gregorian cycle */
	static const Year years_in_gregorian_cycle = 400;
	#define days_in_gregorian_cycle ((365 * 400) + 100 - 4 + 1)
	static const Time64_T seconds_in_gregorian_cycle = days_in_gregorian_cycle * 60LL * 60LL * 24LL;

	/* Year range we can trust the time funcitons with */
	#define MAX_SAFE_YEAR 2037
	#define MIN_SAFE_YEAR 1971

	/* 28 year Julian calendar cycle */
	#define SOLAR_CYCLE_LENGTH 28

	/* Year cycle from MAX_SAFE_YEAR down. */
	static const short safe_years_high[SOLAR_CYCLE_LENGTH] = {
	2016, 2017, 2018, 2019,
	2020, 2021, 2022, 2023,
	2024, 2025, 2026, 2027,
	2028, 2029, 2030, 2031,
	2032, 2033, 2034, 2035,
	2036, 2037, 2010, 2011,
	2012, 2013, 2014, 2015
	};

	/* Year cycle from MIN_SAFE_YEAR up */
	static const int safe_years_low[SOLAR_CYCLE_LENGTH] = {
	1996, 1997, 1998, 1971,
	1972, 1973, 1974, 1975,
	1976, 1977, 1978, 1979,
	1980, 1981, 1982, 1983,
	1984, 1985, 1986, 1987,
	1988, 1989, 1990, 1991,
	1992, 1993, 1994, 1995,
	};

	/* This isn't used, but it's handy to look at */
	#if 0
	static const char dow_year_start[SOLAR_CYCLE_LENGTH] = {
	5, 0, 1, 2, /* 0 2016 - 2019 */
	3, 5, 6, 0, /* 4 */
	1, 3, 4, 5, /* 8 1996 - 1998, 1971*/
	6, 1, 2, 3, /* 12 1972 - 1975 */
	4, 6, 0, 1, /* 16 */
	2, 4, 5, 6, /* 20 2036, 2037, 2010, 2011 */
	0, 2, 3, 4 /* 24 2012, 2013, 2014, 2015 */
	};
	#endif

	/* Let's assume people are going to be looking for dates in the future.
	Let's provide some cheats so you can skip ahead.
	This has a 4x speed boost when near 2008.
	*/
	/* Number of days since epoch on Jan 1st, 2008 GMT */
	#define CHEAT_DAYS (1199145600 / 24 / 60 / 60)
	#define CHEAT_YEARS 108

	#define IS_LEAP(n) ((!(((n) + 1900) % 400) \|\| (!(((n) + 1900) % 4) && (((n) + 1900) % 100))) != 0)
	#define WRAP(a,b,m) ((a) = ((a) < 0 ) ? ((b)--, (a) + (m)) : (a))

	#ifdef USE_SYSTEM_LOCALTIME
	# define SHOULD_USE_SYSTEM_LOCALTIME(a) ( \
	(a) <= SYSTEM_LOCALTIME_MAX && \
	(a) >= SYSTEM_LOCALTIME_MIN \
	)
	#else
	# define SHOULD_USE_SYSTEM_LOCALTIME(a) (0)
	#endif

	#ifdef USE_SYSTEM_GMTIME
	# define SHOULD_USE_SYSTEM_GMTIME(a) ( \
	(a) <= SYSTEM_GMTIME_MAX && \
	(a) >= SYSTEM_GMTIME_MIN \
	)
	#else
	# define SHOULD_USE_SYSTEM_GMTIME(a) (0)
	#endif

	/* Multi varadic macros are a C99 thing, alas */
	#ifdef TIME_64_DEBUG
	# define TIME64_TRACE(format) (fprintf(stderr, format))
	# define TIME64_TRACE1(format, var1) (fprintf(stderr, format, var1))
	# define TIME64_TRACE2(format, var1, var2) (fprintf(stderr, format, var1, var2))
	# define TIME64_TRACE3(format, var1, var2, var3) (fprintf(stderr, format, var1, var2, var3))
	#else
	# define TIME64_TRACE(format) ((void)0)
	# define TIME64_TRACE1(format, var1) ((void)0)
	# define TIME64_TRACE2(format, var1, var2) ((void)0)
	# define TIME64_TRACE3(format, var1, var2, var3) ((void)0)
	#endif


	static int is_exception_century(Year year)
	{
	int is_exception = ((year % 100 == 0) && !(year % 400 == 0));
	TIME64_TRACE1("# is_exception_century: %s\n", is_exception ? "yes" : "no");

	return(is_exception);
	}


	/* Compare two dates.
	The result is like cmp.
	Ignores things like gmtoffset and dst
	*/
	static int cmp_date( const struct TM* left, const struct tm* right ) {
	if( left->tm_year > right->tm_year )
	return 1;
	if( left->tm_year < right->tm_year )
	return -1;
	if( left->tm_mon > right->tm_mon )
	return 1;
	if( left->tm_mon < right->tm_mon )
	return -1;
	if( left->tm_mday > right->tm_mday )
	return 1;
	if( left->tm_mday < right->tm_mday )
	return -1;
	if( left->tm_hour > right->tm_hour )
	return 1;
	if( left->tm_hour < right->tm_hour )
	return -1;
	if( left->tm_min > right->tm_min )
	return 1;
	if( left->tm_min < right->tm_min )
	return -1;
	if( left->tm_sec > right->tm_sec )
	return 1;
	if( left->tm_sec < right->tm_sec )
	return -1;
	return 0;
	}


	/* Check if a date is safely inside a range.
	The intention is to check if its a few days inside.
	*/
	static int date_in_safe_range( const struct TM* date, const struct tm* min, const struct tm* max ) {
	if( cmp_date(date, min) == -1 )
	return 0;

	if( cmp_date(date, max) == 1 )
	return 0;

	return 1;
	}


	/* timegm() is not in the C or POSIX spec, but it is such a useful
	extension I would be remiss in leaving it out. Also I need it
	for localtime64()
	*/
	Time64_T timegm64(const struct TM *date) {
	Time64_T days = 0;
	Time64_T seconds = 0;
	Year year;
	Year orig_year = (Year)date->tm_year;
	int cycles = 0;

	if( (orig_year > 100) \|\| (orig_year < -300) ) {
	cycles = (orig_year - 100) / 400;
	orig_year -= cycles * 400;
	days += (Time64_T)cycles * days_in_gregorian_cycle;
	}
	TIME64_TRACE3("# timegm/ cycles: %d, days: %lld, orig_year: %lld\n", cycles, days, orig_year);

	if( orig_year > 70 ) {
	year = 70;
	while( year < orig_year ) {
	days += length_of_year[IS_LEAP(year)];
	year++;
	}
	}
	else if ( orig_year < 70 ) {
	year = 69;
	do {
	days -= length_of_year[IS_LEAP(year)];
	year--;
	} while( year >= orig_year );
	}

	days += julian_days_by_month[IS_LEAP(orig_year)][date->tm_mon];
	days += date->tm_mday - 1;

	seconds = days * 60 * 60 * 24;

	seconds += date->tm_hour * 60 * 60;
	seconds += date->tm_min * 60;
	seconds += date->tm_sec;

	return(seconds);
	}


	static int check_tm(struct TM *tm)
	{
	/* Don't forget leap seconds */
	assert(tm->tm_sec >= 0);
	assert(tm->tm_sec <= 61);

	assert(tm->tm_min >= 0);
	assert(tm->tm_min <= 59);

	assert(tm->tm_hour >= 0);
	assert(tm->tm_hour <= 23);

	assert(tm->tm_mday >= 1);
	assert(tm->tm_mday <= days_in_month[IS_LEAP(tm->tm_year)][tm->tm_mon]);

	assert(tm->tm_mon >= 0);
	assert(tm->tm_mon <= 11);

	assert(tm->tm_wday >= 0);
	assert(tm->tm_wday <= 6);

	assert(tm->tm_yday >= 0);
	assert(tm->tm_yday <= length_of_year[IS_LEAP(tm->tm_year)]);

	#ifdef HAVE_TM_TM_GMTOFF
	assert(tm->tm_gmtoff >= -24 * 60 * 60);
	assert(tm->tm_gmtoff <= 24 * 60 * 60);
	#endif

	return 1;
	}


	/* The exceptional centuries without leap years cause the cycle to
	shift by 16
	*/
	static Year cycle_offset(Year year)
	{
	const Year start_year = 2000;
	Year year_diff = year - start_year;
	Year exceptions;

	if( year > start_year )
	year_diff--;

	exceptions = year_diff / 100;
	exceptions -= year_diff / 400;

	TIME64_TRACE3("# year: %lld, exceptions: %lld, year_diff: %lld\n",
	year, exceptions, year_diff);

	return exceptions * 16;
	}

	/* For a given year after 2038, pick the latest possible matching
	year in the 28 year calendar cycle.

	A matching year...
	1) Starts on the same day of the week.
	2) Has the same leap year status.

	This is so the calendars match up.

	Also the previous year must match. When doing Jan 1st you might
	wind up on Dec 31st the previous year when doing a -UTC time zone.

	Finally, the next year must have the same start day of week. This
	is for Dec 31st with a +UTC time zone.
	It doesn't need the same leap year status since we only care about
	January 1st.
	*/
	static int safe_year(const Year year)
	{
	int _safe_year = (int)year;
	Year year_cycle;

	if( year >= MIN_SAFE_YEAR && year <= MAX_SAFE_YEAR ) {
	return _safe_year;
	}

	year_cycle = year + cycle_offset(year);

	/* safe_years_low is off from safe_years_high by 8 years */
	if( year < MIN_SAFE_YEAR )
	year_cycle -= 8;

	/* Change non-leap xx00 years to an equivalent */
	if( is_exception_century(year) )
	year_cycle += 11;

	/* Also xx01 years, since the previous year will be wrong */
	if( is_exception_century(year - 1) )
	year_cycle += 17;

	year_cycle %= SOLAR_CYCLE_LENGTH;
	if( year_cycle < 0 )
	year_cycle = SOLAR_CYCLE_LENGTH + year_cycle;

	assert( year_cycle >= 0 );
	assert( year_cycle < SOLAR_CYCLE_LENGTH );
	if( year < MIN_SAFE_YEAR )
	_safe_year = safe_years_low[year_cycle];
	else if( year > MAX_SAFE_YEAR )
	_safe_year = safe_years_high[year_cycle];
	else
	assert(0);

	TIME64_TRACE3("# year: %lld, year_cycle: %lld, safe_year: %d\n",
	year, year_cycle, _safe_year);

	assert(_safe_year <= MAX_SAFE_YEAR && _safe_year >= MIN_SAFE_YEAR);

	return _safe_year;
	}


	void copy_tm_to_TM64(const struct tm src, struct TM dest) {
	if( src == NULL ) {
	memset(dest, 0, sizeof(*dest));
	}
	else {
	# ifdef USE_TM64
	dest->tm_sec = src->tm_sec;
	dest->tm_min = src->tm_min;
	dest->tm_hour = src->tm_hour;
	dest->tm_mday = src->tm_mday;
	dest->tm_mon = src->tm_mon;
	dest->tm_year = (Year)src->tm_year;
	dest->tm_wday = src->tm_wday;
	dest->tm_yday = src->tm_yday;
	dest->tm_isdst = src->tm_isdst;

	# ifdef HAVE_TM_TM_GMTOFF
	dest->tm_gmtoff = src->tm_gmtoff;
	# endif

	# ifdef HAVE_TM_TM_ZONE
	dest->tm_zone = src->tm_zone;
	# endif

	# else
	/* They're the same type */
	memcpy(dest, src, sizeof(*dest));
	# endif
	}
	}


	void copy_TM64_to_tm(const struct TM src, struct tm dest) {
	if( src == NULL ) {
	memset(dest, 0, sizeof(*dest));
	}
	else {
	# ifdef USE_TM64
	dest->tm_sec = src->tm_sec;
	dest->tm_min = src->tm_min;
	dest->tm_hour = src->tm_hour;
	dest->tm_mday = src->tm_mday;
	dest->tm_mon = src->tm_mon;
	dest->tm_year = (int)src->tm_year;
	dest->tm_wday = src->tm_wday;
	dest->tm_yday = src->tm_yday;
	dest->tm_isdst = src->tm_isdst;

	# ifdef HAVE_TM_TM_GMTOFF
	dest->tm_gmtoff = src->tm_gmtoff;
	# endif

	# ifdef HAVE_TM_TM_ZONE
	dest->tm_zone = src->tm_zone;
	# endif

	# else
	/* They're the same type */
	memcpy(dest, src, sizeof(*dest));
	# endif
	}
	}


	#ifndef HAVE_LOCALTIME_R
	/* Simulate localtime_r() to the best of our ability */
	static struct tm * fake_localtime_r(const time_t time, struct tm result) {
	const struct tm *static_result = localtime(time);

	assert(result != NULL);

	if( static_result == NULL ) {
	memset(result, 0, sizeof(*result));
	return NULL;
	}
	else {
	memcpy(result, static_result, sizeof(*result));
	return result;
	}
	}
	#endif


	#ifndef HAVE_GMTIME_R
	/* Simulate gmtime_r() to the best of our ability */
	static struct tm * fake_gmtime_r(const time_t time, struct tm result) {
	const struct tm *static_result = gmtime(time);

	assert(result != NULL);

	if( static_result == NULL ) {
	memset(result, 0, sizeof(*result));
	return NULL;
	}
	else {
	memcpy(result, static_result, sizeof(*result));
	return result;
	}
	}
	#endif


	static Time64_T seconds_between_years(Year left_year, Year right_year) {
	int increment = (left_year > right_year) ? 1 : -1;
	Time64_T seconds = 0;
	int cycles;

	if( left_year > 2400 ) {
	cycles = (left_year - 2400) / 400;
	left_year -= cycles * 400;
	seconds += cycles * seconds_in_gregorian_cycle;
	}
	else if( left_year < 1600 ) {
	cycles = (left_year - 1600) / 400;
	left_year += cycles * 400;
	seconds += cycles * seconds_in_gregorian_cycle;
	}

	while( left_year != right_year ) {
	seconds += length_of_year[IS_LEAP(right_year - 1900)] * 60 * 60 * 24;
	right_year += increment;
	}

	return seconds * increment;
	}


	Time64_T mktime64(struct TM *input_date) {
	struct tm safe_date;
	struct TM date;
	Time64_T timev;
	Year year = input_date->tm_year + 1900;

	if( date_in_safe_range(input_date, &SYSTEM_MKTIME_MIN, &SYSTEM_MKTIME_MAX) )
	{
	copy_TM64_to_tm(input_date, &safe_date);
	timev = (Time64_T)mktime(&safe_date);

	/* Correct the possibly out of bound input date */
	copy_tm_to_TM64(&safe_date, input_date);
	return timev;
	}

	/* Have to make the year safe in date else it won't fit in safe_date */
	date = *input_date;
	date.tm_year = safe_year(year) - 1900;
	copy_TM64_to_tm(&date, &safe_date);

	timev = (Time64_T)mktime(&safe_date);

	/* Correct the user's possibly out of bound input date */
	copy_tm_to_TM64(&safe_date, input_date);

	timev += seconds_between_years(year, (Year)(safe_date.tm_year) + 1900);

	return timev;
	}


	/* Because I think mktime() is a crappy name */
	Time64_T timelocal64(struct TM *date) {
	return mktime64(date);
	}


	struct TM gmtime64_r (const Time64_T in_time, struct TM *p)
	{
	int v_tm_sec, v_tm_min, v_tm_hour, v_tm_mon, v_tm_wday;
	Time64_T v_tm_tday;
	int leap;
	Time64_T m;
	Time64_T timev = *in_time;
	Year year = 70;
	int cycles = 0;

	assert(p != NULL);

	/* Use the system gmtime() if time_t is small enough */
	if( SHOULD_USE_SYSTEM_GMTIME(*in_time) ) {
	time_t safe_time = (time_t)*in_time;
	struct tm safe_date;
	GMTIME_R(&safe_time, &safe_date);

	copy_tm_to_TM64(&safe_date, p);
	assert(check_tm(p));

	return p;
	}

	#ifdef HAVE_TM_TM_GMTOFF
	p->tm_gmtoff = 0;
	#endif
	p->tm_isdst = 0;

	#ifdef HAVE_TM_TM_ZONE
	p->tm_zone = (char*)"UTC";
	#endif

	v_tm_sec = (int)(timev % 60);
	timev /= 60;
	v_tm_min = (int)(timev % 60);
	timev /= 60;
	v_tm_hour = (int)(timev % 24);
	timev /= 24;
	v_tm_tday = timev;

	WRAP (v_tm_sec, v_tm_min, 60);
	WRAP (v_tm_min, v_tm_hour, 60);
	WRAP (v_tm_hour, v_tm_tday, 24);

	v_tm_wday = (int)((v_tm_tday + 4) % 7);
	if (v_tm_wday < 0)
	v_tm_wday += 7;
	m = v_tm_tday;

	if (m >= CHEAT_DAYS) {
	year = CHEAT_YEARS;
	m -= CHEAT_DAYS;
	}

	if (m >= 0) {
	/* Gregorian cycles, this is huge optimization for distant times */
	cycles = (int)(m / (Time64_T) days_in_gregorian_cycle);
	if( cycles ) {
	m -= (cycles * (Time64_T) days_in_gregorian_cycle);
	year += (cycles * years_in_gregorian_cycle);
	}

	/* Years */
	leap = IS_LEAP (year);
	while (m >= (Time64_T) length_of_year[leap]) {
	m -= (Time64_T) length_of_year[leap];
	year++;
	leap = IS_LEAP (year);
	}

	/* Months */
	v_tm_mon = 0;
	while (m >= (Time64_T) days_in_month[leap][v_tm_mon]) {
	m -= (Time64_T) days_in_month[leap][v_tm_mon];
	v_tm_mon++;
	}
	} else {
	year--;

	/* Gregorian cycles */
	cycles = (int)((m / (Time64_T) days_in_gregorian_cycle) + 1);
	if( cycles ) {
	m -= (cycles * (Time64_T) days_in_gregorian_cycle);
	year += (cycles * years_in_gregorian_cycle);
	}

	/* Years */
	leap = IS_LEAP (year);
	while (m < (Time64_T) -length_of_year[leap]) {
	m += (Time64_T) length_of_year[leap];
	year--;
	leap = IS_LEAP (year);
	}

	/* Months */
	v_tm_mon = 11;
	while (m < (Time64_T) -days_in_month[leap][v_tm_mon]) {
	m += (Time64_T) days_in_month[leap][v_tm_mon];
	v_tm_mon--;
	}
	m += (Time64_T) days_in_month[leap][v_tm_mon];
	}

	p->tm_year = year;
	if( p->tm_year != year ) {
	#ifdef EOVERFLOW
	errno = EOVERFLOW;
	#endif
	return NULL;
	}

	/* At this point m is less than a year so casting to an int is safe */
	p->tm_mday = (int) m + 1;
	p->tm_yday = julian_days_by_month[leap][v_tm_mon] + (int)m;
	p->tm_sec = v_tm_sec;
	p->tm_min = v_tm_min;
	p->tm_hour = v_tm_hour;
	p->tm_mon = v_tm_mon;
	p->tm_wday = v_tm_wday;

	assert(check_tm(p));

	return p;
	}


	struct TM localtime64_r (const Time64_T timev, struct TM *local_tm)
	{
	time_t safe_time;
	struct tm safe_date;
	struct TM gm_tm;
	Year orig_year;
	int month_diff;

	assert(local_tm != NULL);

	/* Use the system localtime() if time_t is small enough */
	if( SHOULD_USE_SYSTEM_LOCALTIME(*timev) ) {
	safe_time = (time_t)*timev;

	TIME64_TRACE1("Using system localtime for %lld\n", *timev);

	LOCALTIME_R(&safe_time, &safe_date);

	copy_tm_to_TM64(&safe_date, local_tm);
	assert(check_tm(local_tm));

	return local_tm;
	}

	if( gmtime64_r(timev, &gm_tm) == NULL ) {
	TIME64_TRACE1("gmtime64_r returned null for %lld\n", *timev);
	return NULL;
	}

	orig_year = gm_tm.tm_year;

	if (gm_tm.tm_year > (2037 - 1900) \|\|
	gm_tm.tm_year < (1970 - 1900)
	)
	{
	TIME64_TRACE1("Mapping tm_year %lld to safe_year\n", (Year)gm_tm.tm_year);
	gm_tm.tm_year = safe_year((Year)(gm_tm.tm_year) + 1900) - 1900;
	}

	safe_time = (time_t)timegm64(&gm_tm);
	if( LOCALTIME_R(&safe_time, &safe_date) == NULL ) {
	TIME64_TRACE1("localtime_r(%d) returned NULL\n", (int)safe_time);
	return NULL;
	}

	copy_tm_to_TM64(&safe_date, local_tm);

	local_tm->tm_year = orig_year;
	if( local_tm->tm_year != orig_year ) {
	TIME64_TRACE2("tm_year overflow: tm_year %lld, orig_year %lld\n",
	(Year)local_tm->tm_year, (Year)orig_year);

	#ifdef EOVERFLOW
	errno = EOVERFLOW;
	#endif
	return NULL;
	}


	month_diff = local_tm->tm_mon - gm_tm.tm_mon;

	/* When localtime is Dec 31st previous year and
	gmtime is Jan 1st next year.
	*/
	if( month_diff == 11 ) {
	local_tm->tm_year--;
	}

	/* When localtime is Jan 1st, next year and
	gmtime is Dec 31st, previous year.
	*/
	if( month_diff == -11 ) {
	local_tm->tm_year++;
	}

	/* GMT is Jan 1st, xx01 year, but localtime is still Dec 31st
	in a non-leap xx00. There is one point in the cycle
	we can't account for which the safe xx00 year is a leap
	year. So we need to correct for Dec 31st comming out as
	the 366th day of the year.
	*/
	if( !IS_LEAP(local_tm->tm_year) && local_tm->tm_yday == 365 )
	local_tm->tm_yday--;

	assert(check_tm(local_tm));

	return local_tm;
	}


	static int valid_tm_wday( const struct TM* date ) {
	if( 0 <= date->tm_wday && date->tm_wday <= 6 )
	return 1;

	return 0;
	}

	static int valid_tm_mon( const struct TM* date ) {
	if( 0 <= date->tm_mon && date->tm_mon <= 11 )
	return 1;

	return 0;
	}


	char asctime64_r( const struct TM date, char *result ) {
	/* I figure everything else can be displayed, even hour 25, but if
	these are out of range we walk off the name arrays */
	if( !valid_tm_wday(date) \|\| !valid_tm_mon(date) )
	return NULL;

	sprintf(result, TM64_ASCTIME_FORMAT,
	wday_name[date->tm_wday],
	mon_name[date->tm_mon],
	date->tm_mday, date->tm_hour,
	date->tm_min, date->tm_sec,
	1900 + date->tm_year);

	return result;
	}


	char ctime64_r( const Time64_T timev, char* result ) {
	struct TM date;

	if (!localtime64_r( timev, &date ))
	return NULL;

	return asctime64_r( &date, result );
	}