diff --git a/mimetreeparser/autotests/basicobjecttreeparsertest.cpp b/mimetreeparser/autotests/basicobjecttreeparsertest.cpp
--- a/mimetreeparser/autotests/basicobjecttreeparsertest.cpp
+++ b/mimetreeparser/autotests/basicobjecttreeparsertest.cpp
@@ -38,6 +38,7 @@
 void ObjectTreeParserTest::initTestCase()
 {
     Test::setupEnv();
+    qputenv("TZ", "GMT");
 }
 
 QString stringifyMessagePartTree(const MimeTreeParser::MessagePart::Ptr &messagePart, QString indent)