Set date.timezone to UTC.

src/deb/php/php.ini

@@ -944,7 +944,7 @@ cli_server.color = On
 [Date]
 ; Defines the default timezone used by the date functions
 ; http://php.net/date.timezone
-;date.timezone =
+date.timezone = UTC
 
 ; http://php.net/date.default-latitude
 ;date.default_latitude = 31.7667