diff --git a/date.c b/date.c
index 7365a4ad24..bee9fe8f10 100644
--- a/date.c
+++ b/date.c
@@ -868,6 +868,10 @@ static int match_object_header_date(const char *date, timestamp_t *timestamp, in
 	return 0;
 }
 
+
+/* timestamp of 2099-12-31T23:59:59Z, including 32 leap days */
+static const timestamp_t timestamp_max = (((timestamp_t)2100 - 1970) * 365 + 32) * 24 * 60 * 60 - 1;
+
 /* 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. */
 int parse_date_basic(const char *date, timestamp_t *timestamp, int *offset)
@@ -937,8 +941,14 @@ int parse_date_basic(const char *date, timestamp_t *timestamp, int *offset)
 		}
 	}
 
-	if (!tm_gmt)
+	if (!tm_gmt) {
+		if (*offset > 0 && *offset * 60 > *timestamp)
+			return -1;
+		if (*offset < 0 && -*offset * 60 > timestamp_max - *timestamp)
+			return -1;
 		*timestamp -= *offset * 60;
+	}
+
 	return 0; /* success */
 }
 
diff --git a/t/t0006-date.sh b/t/t0006-date.sh
index 24e8647f26..fd373e1b39 100755
--- a/t/t0006-date.sh
+++ b/t/t0006-date.sh
@@ -123,6 +123,39 @@ check_parse '2008-02-14 20:30:45 -05:00' '2008-02-14 20:30:45 -0500'
 check_parse '2008-02-14 20:30:45' '2008-02-14 20:30:45 -0500' EST5
 check_parse 'Thu, 7 Apr 2005 15:14:13 -0700' '2005-04-07 15:14:13 -0700'
 
+check_parse '1970-01-01 00:00:00' '1970-01-01 00:00:00 +0000'
+check_parse '1970-01-01 00:00:00 +00' '1970-01-01 00:00:00 +0000'
+check_parse '1970-01-01 00:00:00 Z' '1970-01-01 00:00:00 +0000'
+check_parse '1970-01-01 00:00:00 -01' '1970-01-01 00:00:00 -0100'
+check_parse '1970-01-01 00:00:00 +01' bad
+check_parse '1970-01-01 00:00:00 +11' bad
+check_parse '1970-01-01 00:59:59 +01' bad
+check_parse '1970-01-01 01:00:00 +01' '1970-01-01 01:00:00 +0100'
+check_parse '1970-01-01 01:00:00 +11' bad
+check_parse '1970-01-02 00:00:00 +11' '1970-01-02 00:00:00 +1100'
+check_parse '1969-12-31 23:59:59' bad
+check_parse '1969-12-31 23:59:59 +00' bad
+check_parse '1969-12-31 23:59:59 Z' bad
+check_parse '1969-12-31 23:59:59 +11' bad
+check_parse '1969-12-31 23:59:59 -11' bad
+
+REQUIRE_64BIT_TIME=HAVE_64BIT_TIME
+check_parse '2099-12-31 23:59:59' '2099-12-31 23:59:59 +0000'
+check_parse '2099-12-31 23:59:59 +00' '2099-12-31 23:59:59 +0000'
+check_parse '2099-12-31 23:59:59 Z' '2099-12-31 23:59:59 +0000'
+check_parse '2099-12-31 23:59:59 +01' '2099-12-31 23:59:59 +0100'
+check_parse '2099-12-31 23:59:59 -01' bad
+check_parse '2099-12-31 23:59:59 -11' bad
+check_parse '2099-12-31 23:00:00 -01' bad
+check_parse '2099-12-31 22:59:59 -01' '2099-12-31 22:59:59 -0100'
+check_parse '2100-00-00 00:00:00' bad
+check_parse '2099-12-30 00:00:00 -11' '2099-12-30 00:00:00 -1100'
+check_parse '2100-00-00 00:00:00 +00' bad
+check_parse '2100-00-00 00:00:00 Z' bad
+check_parse '2100-00-00 00:00:00 -11' bad
+check_parse '2100-00-00 00:00:00 +11' bad
+REQUIRE_64BIT_TIME=
+
 check_approxidate() {
 	echo "$1 -> $2 +0000" >expect
 	test_expect_${3:-success} "parse approxidate ($1)" "