You can change the time zone for your Facebook ad account from Ad account settings. When you change your time zone, this deactivates the existing ad account and stops running any ads on that ad account. You can't reactivate this account. A new ad account will be created with the new time zone. Use this new ad account to run your ads.

Note: If your ad account is a part of Business Manager, you won't be able to update the time zone.

To change the time zone for your ad account:

1. Go to Ads Manager.
2. Click .
3. Click All Tools and select Ad Account Settings. You may need to re-enter your password.
4. In the Account information section, find Time zone and click Change time zone.
5. Click Create New Account. The default time zone for new ad accounts is Pacific Standard Time (PST), so make sure that your ad account's time zone is correct before you create new campaigns.

* Nguồn: Facebook