a wrapper for mktime() call that honours timezone

+/* Copyright (C) 2001 Free Software Foundation, Inc.
+   A wrapper for mktime function allowing to specify the timezone.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <time.h>
+
+/* Convert struct tm into time_t, taking into account timezone offset */
+time_t
+mu_mktime (struct tm *timeptr, int tz)
+{
+  static int mu_timezone;
+  
+  if (mu_timezone == 0)
+    {
+	struct tm *tm;
+	time_t t = 0;
+	tm = gmtime(&t);
+	mu_timezone = mktime(tm);
+    }
+  return mktime(timeptr) - mu_timezone + tz;
+}