Each reseller account can set their own default time zone, which will affect the delivery of every campaign that goes out. The admin account’s default timezone sets the default for all new accounts and account users created under it.
To set your default time zone, go to Settings > Your Site Settings > Sign Up Settings > Default Sign Up Country, State/Province, Time Zone
Each end-user also has the ability of adjusting their time zone if different from the one set by the account admin. When viewing an account, you will be viewing it in the timezone relative to the current user’s timezone.
To change the end-user time zone, hover over the end-user name on the top right menu options of the user’s account and click on Edit Information.