diff --git a/builtin/commit.c b/builtin/commit.c
index eba1377eb3..2deccb5444 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -543,6 +543,7 @@ static void determine_author_info(struct strbuf *author_ident)
 
 	if (author_message) {
 		const char *a, *lb, *rb, *eol;
+		size_t len;
 
 		a = strstr(author_message_buffer, "\nauthor ");
 		if (!a)
@@ -563,6 +564,11 @@ static void determine_author_info(struct strbuf *author_ident)
 					 (a + strlen("\nauthor "))));
 		email = xmemdupz(lb + strlen("<"), rb - (lb + strlen("<")));
 		date = xmemdupz(rb + strlen("> "), eol - (rb + strlen("> ")));
+		len = eol - (rb + strlen("> "));
+		date = xmalloc(len + 2);
+		*date = '@';
+		memcpy(date + 1, rb + strlen("> "), len);
+		date[len + 1] = '\0';
 	}
 
 	if (force_author) {
diff --git a/date.c b/date.c
index 353e0a5e53..a5055ca09d 100644
--- a/date.c
+++ b/date.c
@@ -597,6 +597,33 @@ static int date_string(unsigned long date, int offset, char *buf, int len)
 	return snprintf(buf, len, "%lu %c%02d%02d", date, sign, offset / 60, offset % 60);
 }
 
+/*
+ * Parse a string like "0 +0000" as ancient timestamp near epoch, but
+ * only when it appears not as part of any other string.
+ */
+static int match_object_header_date(const char *date, unsigned long *timestamp, int *offset)
+{
+	char *end;
+	unsigned long stamp;
+	int ofs;
+
+	if (*date < '0' || '9' <= *date)
+		return -1;
+	stamp = strtoul(date, &end, 10);
+	if (*end != ' ' || stamp == ULONG_MAX || (end[1] != '+' && end[1] != '-'))
+		return -1;
+	date = end + 2;
+	ofs = strtol(date, &end, 10);
+	if ((*end != '\0' && (*end != '\n')) || end != date + 4)
+		return -1;
+	ofs = (ofs / 100) * 60 + (ofs % 100);
+	if (date[-1] == '-')
+		ofs = -ofs;
+	*timestamp = stamp;
+	*offset = ofs;
+	return 0;
+}
+
 /* 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, unsigned long *timestamp, int *offset)
@@ -622,6 +649,9 @@ int parse_date_basic(const char *date, unsigned long *timestamp, int *offset)
 	*offset = -1;
 	tm_gmt = 0;
 
+	if (*date == '@' &&
+	    !match_object_header_date(date + 1, timestamp, offset))
+		return 0; /* success */
 	for (;;) {
 		int match = 0;
 		unsigned char c = *date;
diff --git a/git-sh-setup.sh b/git-sh-setup.sh
index 1fba6c2de0..5d8e4e6c89 100644
--- a/git-sh-setup.sh
+++ b/git-sh-setup.sh
@@ -200,7 +200,7 @@ get_author_ident_from_commit () {
 		s/.*/GIT_AUTHOR_EMAIL='\''&'\''/p
 
 		g
-		s/^author [^<]* <[^>]*> \(.*\)$/\1/
+		s/^author [^<]* <[^>]*> \(.*\)$/@\1/
 		s/.*/GIT_AUTHOR_DATE='\''&'\''/p
 
 		q
diff --git a/t/t3400-rebase.sh b/t/t3400-rebase.sh
index c355533236..e647272a01 100755
--- a/t/t3400-rebase.sh
+++ b/t/t3400-rebase.sh
@@ -218,4 +218,27 @@ test_expect_success 'rebase -m can copy notes' '
 	test "a note" = "$(git notes show HEAD)"
 '
 
+test_expect_success 'rebase commit with an ancient timestamp' '
+	git reset --hard &&
+
+	>old.one && git add old.one && test_tick &&
+	git commit --date="@12345 +0400" -m "Old one" &&
+	>old.two && git add old.two && test_tick &&
+	git commit --date="@23456 +0500" -m "Old two" &&
+	>old.three && git add old.three && test_tick &&
+	git commit --date="@34567 +0600" -m "Old three" &&
+
+	git cat-file commit HEAD^^ >actual &&
+	grep "author .* 12345 +0400$" actual &&
+	git cat-file commit HEAD^ >actual &&
+	grep "author .* 23456 +0500$" actual &&
+	git cat-file commit HEAD >actual &&
+	grep "author .* 34567 +0600$" actual &&
+
+	git rebase --onto HEAD^^ HEAD^ &&
+
+	git cat-file commit HEAD >actual &&
+	grep "author .* 34567 +0600$" actual
+'
+
 test_done