diff --git a/google/internal/externalaccount/basecredentials.go b/google/internal/externalaccount/basecredentials.go
index 1b87c09..1a6e93c 100644
--- a/google/internal/externalaccount/basecredentials.go
+++ b/google/internal/externalaccount/basecredentials.go
@@ -14,7 +14,9 @@
 )
 
 // now aliases time.Now for testing
-var now = time.Now
+var now = func() time.Time {
+	return time.Now().UTC()
+}
 
 // Config stores the configuration for fetching tokens with external credentials.
 type Config struct {