Print debug error message when encoutering invalid PLIST_DATE values

diff --git a/src/jplist.c b/src/jplist.c
index dd2e36a..c29f760 100644
--- a/src/jplist.c
+++ b/src/jplist.c

@@ -259,6 +259,7 @@
         if (coerce) {
             Time64_T timev;
             if (plist_real_to_time64(node_data->realval, &timev) < 0) {
+                PLIST_JSON_WRITE_ERR("Encountered invalid date value %f\n", node_data->realval);
                 return PLIST_ERR_INVALID_ARG;
             }
             struct TM _btime;

diff --git a/src/oplist.c b/src/oplist.c
index 4b3b666..77a99cd 100644
--- a/src/oplist.c
+++ b/src/oplist.c

@@ -303,6 +303,7 @@
         if (coerce) {
             Time64_T timev;
             if (plist_real_to_time64(node_data->realval, &timev) < 0) {
+                PLIST_OSTEP_WRITE_ERR("Encountered invalid date value %f\n", node_data->realval);
                 return PLIST_ERR_INVALID_ARG;
             }
             struct TM _btime;

diff --git a/src/out-default.c b/src/out-default.c
index 87689d1..13b9d9c 100644
--- a/src/out-default.c
+++ b/src/out-default.c

@@ -233,6 +233,9 @@
         {
             Time64_T timev;
             if (plist_real_to_time64(node_data->realval, &timev) < 0) {
+#if DEBUG
+                fprintf(stderr, "libplist: ERROR: Encountered invalid date value %f\n", node_data->realval);
+#endif
                 return PLIST_ERR_INVALID_ARG;
             }
             struct TM _btime;

diff --git a/src/out-limd.c b/src/out-limd.c
index e47ca0c..83a5e26 100644
--- a/src/out-limd.c
+++ b/src/out-limd.c

@@ -222,6 +222,9 @@
         {
             Time64_T timev;
             if (plist_real_to_time64(node_data->realval, &timev) < 0) {
+#if DEBUG
+                fprintf(stderr, "libplist: ERROR: Encountered invalid date value %f\n", node_data->realval);
+#endif
                 return PLIST_ERR_INVALID_ARG;
             }
             struct TM _btime;

diff --git a/src/out-plutil.c b/src/out-plutil.c
index 3b5bd34..e603f31 100644
--- a/src/out-plutil.c
+++ b/src/out-plutil.c

@@ -239,6 +239,9 @@
         {
             Time64_T timev;
             if (plist_real_to_time64(node_data->realval, &timev) < 0) {
+#if DEBUG
+                fprintf(stderr, "libplist: ERROR: Encountered invalid date value %f\n", node_data->realval);
+#endif
                 return PLIST_ERR_INVALID_ARG;
             }
             struct TM _btime;

diff --git a/src/xplist.c b/src/xplist.c
index 3157ab0..b2c134e 100644
--- a/src/xplist.c
+++ b/src/xplist.c

@@ -194,6 +194,7 @@
         {
             Time64_T timev;
             if (plist_real_to_time64(node_data->realval, &timev) < 0) {
+                PLIST_XML_WRITE_ERR("Encountered invalid date value %f\n", node_data->realval);
                 return PLIST_ERR_INVALID_ARG;
             }
             struct TM _btime;