return date_string(then, offset, result, maxlen);
 }
 
+enum date_mode parse_date_format(const char *format)
+{
+       if (!strcmp(format, "relative"))
+               return DATE_RELATIVE;
+       else if (!strcmp(format, "iso8601") ||
+                !strcmp(format, "iso"))
+               return DATE_ISO8601;
+       else if (!strcmp(format, "rfc2822") ||
+                !strcmp(format, "rfc"))
+               return DATE_RFC2822;
+       else if (!strcmp(format, "short"))
+               return DATE_SHORT;
+       else if (!strcmp(format, "local"))
+               return DATE_LOCAL;
+       else if (!strcmp(format, "default"))
+               return DATE_NORMAL;
+       else
+               die("unknown date format %s", format);
+}
+
 void datestamp(char *buf, int bufsize)
 {
        time_t now;