diff --git a/scripts/get_source_date_epoch.sh b/scripts/get_source_date_epoch.sh
index 8a41eebae7..d122acf385 100755
--- a/scripts/get_source_date_epoch.sh
+++ b/scripts/get_source_date_epoch.sh
@@ -6,21 +6,23 @@ if [ -n "$TOPDIR" ]; then
 	cd "$TOPDIR" || exit 1
 fi
 
+SOURCE="${1:-.}"
+
 try_version() {
-	[ -f version.date ] || return 1
-	SOURCE_DATE_EPOCH="$(cat version.date)"
+	[ -f "$SOURCE/version.date" ] || return 1
+	SOURCE_DATE_EPOCH=$(cat "$SOURCE/version.date")
 	[ -n "$SOURCE_DATE_EPOCH" ]
 }
 
 try_git() {
-	[ -e .git ] || return 1
-	SOURCE_DATE_EPOCH="$(git log -1 --format=format:%ct)"
+	SOURCE_DATE_EPOCH=$(git -C "$SOURCE" log -1 --format=format:%ct \
+		"$SOURCE" 2>/dev/null)
 	[ -n "$SOURCE_DATE_EPOCH" ]
 }
 
 try_hg() {
-	[ -d .hg ] || return 1
-	SOURCE_DATE_EPOCH="$(hg log --template '{date}' -l 1 | cut -d. -f1)"
+	SOURCE_DATE_EPOCH=$(hg --cwd "$SOURCE" log --template '{date}' -l 1 \
+		"$SOURCE" 2>/dev/null | cut -d. -f1)
 	[ -n "$SOURCE_DATE_EPOCH" ]
 }