By default MantisHub uses Year-Month-Day 24hr time format when displaying time fields in your issues. However it is possible to customize your date format.
To configure the date this, go to Manage - Manage Configuration - Configuration Report and add the below configuration options with your preferred date string. You can use the documentation on the following page to get the string for the date format that you desire: http://php.net/manual/en/function.date.php
All Users, All Projects, short_date_format, string, <date string e.g. d-m-y>
* Short Date will appear on your view issues page and your data exports.
All Users, All Projects, normal_date_format,<date string>
* Normal date appears in issue fields and notes.
All Users, All Projects, complete_date_format,<date string>
And you're done! Now you can go visit a new timezone :)