diff --git a/changelogs/unreleased/42251-explicit-timezone-for-karma.yml b/changelogs/unreleased/42251-explicit-timezone-for-karma.yml
new file mode 100644
index 00000000000..25e0e774c48
--- /dev/null
+++ b/changelogs/unreleased/42251-explicit-timezone-for-karma.yml
@@ -0,0 +1,5 @@
+---
+title: Set timezone for karma to UTC
+merge_request: 16602
+author: Takuya Noguchi
+type: other
diff --git a/config/karma.config.js b/config/karma.config.js
index 9f018d14b8f..a101d35704e 100644
--- a/config/karma.config.js
+++ b/config/karma.config.js
@@ -18,6 +18,8 @@ webpackConfig.devtool = 'cheap-inline-source-map';
 
 // Karma configuration
 module.exports = function(config) {
+  process.env.TZ = 'Etc/UTC';
+
   var progressReporter = process.env.CI ? 'mocha' : 'progress';
 
   var karmaConfig = {