Before you change your time zone, consider how it may impact your existing campaigns.
With a zone change, the absolute timing of your campaign is kept intact.
What does that mean? See the example below:
Initially, you set up your network on Eastern Standard Time (EST). You made a campaign to start on 10/1, which would begin promptly at 12 am on that date.
Later, you change your network to Central Standard Time (CST), which is an hour behind EST. Your saved campaign will start on 9/30 at 11 pm — the same time you initially set, but reflected in the context of the Central Time zone. In the dashboard, the date will simply be reflected as 9/30.
What to Do
If you still want your set campaign to start on 10/1 at 12 am in your new time zone, you should edit the campaign after making the time zone adjustment.
Any new campaigns you create will be created in your new time zone.