Hi @Mitra_Ardron and thank you for reaching out! 
You are correct here. It’s currently not possible to manually change your time zone within Asana as it is determined based on your IP address. You can read more about it here.
We have a thread in the #productfeedback category requesting to manually set and fix timezone. If you haven’t yet, feel free to add your vote and comment to it: Manually set and fix time zone
Have a great day!