PATCH: initialise day of month in datetime module

[Oliver Kiddle <okiddle@yahoo.co.uk>]

Note the following:

  % strftime '%F %T' $(strftime -r '%Y%m' 201507)
  2015-06-30 00:00:00

In a struct tm, tm_mday starts at 1 and not 0 so it is better to
initialise it to 1 so the command above will instead return midnight on
the 1st July.

Oliver

diff --git a/Src/Modules/datetime.c b/Src/Modules/datetime.c
index 63a04dc..d941667 100644
--- a/Src/Modules/datetime.c
+++ b/Src/Modules/datetime.c
@@ -53,10 +53,12 @@ reverse_strftime(char *nam, char **argv, char *scalar, int quiet)
      * to use the current timezone.  This is probably the best guess;
      * it's the one that will cause dates and times output by strftime
      * without the -r option and without an explicit timezone to be
-     * converted back correctly.
+     * converted back correctly. Additionally, tm_mday is set to 1
+     * as that and not 0 corresponds to the first of the month.
      */
     (void)memset(&tm, 0, sizeof(tm));
     tm.tm_isdst = -1;
+    tm.tm_mday = 1;
     endp = strptime(argv[1], argv[0], &tm);
 
     if (!endp) {