diff --git a/grep.c b/grep.c
index 898be6ebfa..8d73995e87 100644
--- a/grep.c
+++ b/grep.c
@@ -720,7 +720,14 @@ static int match_one_pattern(struct grep_pat *p, char *bol, char *eol,
 		if (strncmp(bol, field, len))
 			return 0;
 		bol += len;
-		saved_ch = strip_timestamp(bol, &eol);
+		switch (p->field) {
+		case GREP_HEADER_AUTHOR:
+		case GREP_HEADER_COMMITTER:
+			saved_ch = strip_timestamp(bol, &eol);
+			break;
+		default:
+			break;
+		}
 	}
 
  again:
diff --git a/grep.h b/grep.h
index 8a28a676fc..d54adbe56c 100644
--- a/grep.h
+++ b/grep.h
@@ -29,9 +29,11 @@ enum grep_context {
 
 enum grep_header_field {
 	GREP_HEADER_AUTHOR = 0,
-	GREP_HEADER_COMMITTER
+	GREP_HEADER_COMMITTER,
+
+	/* Must be at the end of the enum */
+	GREP_HEADER_FIELD_MAX
 };
-#define GREP_HEADER_FIELD_MAX (GREP_HEADER_COMMITTER + 1)
 
 struct grep_pat {
 	struct grep_pat *next;
diff --git a/t/t7810-grep.sh b/t/t7810-grep.sh
index 91db352cc7..30eaa9a54b 100755
--- a/t/t7810-grep.sh
+++ b/t/t7810-grep.sh
@@ -628,6 +628,18 @@ test_expect_success 'log --all-match --grep --grep --author takes intersection'
 	test_cmp expect actual
 '
 
+test_expect_success 'log --author does not search in timestamp' '
+	: >expect &&
+	git log --author="$GIT_AUTHOR_DATE" >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'log --committer does not search in timestamp' '
+	: >expect &&
+	git log --committer="$GIT_COMMITTER_DATE" >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'grep with CE_VALID file' '
 	git update-index --assume-unchanged t/t &&
 	rm t/t &&