jokokendil
Can you make sure you are using the Locale Defaults: like on the screenshot, if you have 24 hours time, that might be your issue
After that, I don't know, it may be something is broken in export code.
One thing you can do is back up osTickets files and database. Then download fresh from Osticket.com and replace it with your, if anything is broken in code, it should fix it for you.
Note: if you have done any custom changes you will need to apply back. All your settings and data are in the database.
