I made some custom datetime fields that display the time as saved in the database table. Even if my user has a different tz it will display as show in the database. Since the time was showing as my current tz i just left it as it is. This is one issue since odoo wasn't rendering the correct time.
I found this issue after i changed the server timezone (which is ET). After i updated the time, my custom fields were displaying the wrong time and i didn't find a way back so i had to save this data transformed.
There's a place in odoo where you save those fields timezone. If you know where they are let me know
Also this should be in the documentation, I mean the issue about setting up your timezone before creating custom fields.
