diff --git a/ffmpeg_opt.c b/ffmpeg_opt.c
index a0c977b5a70ff40cf918be0208c8d05aa67f94ef..9fe54fffbfebe116f01aa064b2ef21d108b55d9c 100644
--- a/ffmpeg_opt.c
+++ b/ffmpeg_opt.c
@@ -519,7 +519,7 @@ static int opt_recording_timestamp(void *optctx, const char *opt, const char *ar
     char buf[128];
     int64_t recording_timestamp = parse_time_or_die(opt, arg, 0) / 1E6;
     struct tm time = *gmtime((time_t*)&recording_timestamp);
-    if (!strftime(buf, sizeof(buf), "creation_time=%FT%T%z", &time))
+    if (!strftime(buf, sizeof(buf), "creation_time=%Y-%m-%dT%H:%M:%S%z", &time))
         return -1;
     parse_option(o, "metadata", buf, options);