diff --git a/cache.h b/cache.h
index 7f209794ba..e589918320 100644
--- a/cache.h
+++ b/cache.h
@@ -242,7 +242,7 @@ extern void *read_object_with_reference(const unsigned char *sha1,
 					unsigned char *sha1_ret);
 
 const char *show_date(unsigned long time, int timezone);
-void parse_date(const char *date, char *buf, int bufsize);
+int parse_date(const char *date, char *buf, int bufsize);
 void datestamp(char *buf, int bufsize);
 
 extern int setup_ident(void);
diff --git a/date.c b/date.c
index b46f2ce344..8d7b2eb99f 100644
--- a/date.c
+++ b/date.c
@@ -388,7 +388,7 @@ static int match_tz(const char *date, int *offp)
 
 /* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
    (i.e. English) day/month names, and it doesn't work correctly with %z. */
-void parse_date(const char *date, char *result, int maxlen)
+int parse_date(const char *date, char *result, int maxlen)
 {
 	struct tm tm;
 	int offset, sign, tm_gmt;
@@ -431,7 +431,7 @@ void parse_date(const char *date, char *result, int maxlen)
 		offset = (then - mktime(&tm)) / 60;
 
 	if (then == -1)
-		return;
+		return -1;
 
 	if (!tm_gmt)
 		then -= offset * 60;
@@ -442,7 +442,7 @@ void parse_date(const char *date, char *result, int maxlen)
 		sign = '-';
 	}
 
-	snprintf(result, maxlen, "%lu %c%02d%02d", then, sign, offset/60, offset % 60);
+	return snprintf(result, maxlen, "%lu %c%02d%02d", then, sign, offset/60, offset % 60);
 }
 
 void datestamp(char *buf, int bufsize)