diff --git a/bedstead.c b/bedstead.c
index d524564..704ed40 100644
--- a/bedstead.c
+++ b/bedstead.c
@@ -3145,9 +3145,11 @@ fullname_to_fontname(char const *fullname)
 static char *
 time_for_ttx(void)
 {
+	static char timestr[25];
+	size_t timestrlen;
 	struct tm *timeptr, tm;
 	unsigned long long epochull;
-	char *epochstr, *endptr, *timestr;
+	char *epochstr, *endptr;
 
 	/* Work out what timestamp to use. */
 	if ((epochstr = getenv("SOURCE_DATE_EPOCH")) != NULL) {
@@ -3201,9 +3203,8 @@ time_for_ttx(void)
 			return NULL;
 		}
 	}
-	timestr = asctime(timeptr);
-	assert(strlen(timestr) == 25);
-	timestr[24] = '\0'; /* Remove newline. */
+	timestrlen = strftime(timestr, lenof(timestr), "%c", timeptr);
+	assert(timestrlen == 24);
 	return timestr;
 }