When you set up your Smartsheet account, you can change your time zone in Account > Personal Settings > Settings> Time Zone.
But if your account is set up via sharing -- someone shares an object with you and you respond to an email asking you to create an account -- the time zone is set to the time zone from whence the request originated. If you’re not in the same time zone as the person who originated the sharing request, you can reset the time zone in Personal Settings.
Time zones and sheets
Smartsheet may change the time zone of a shared sheet if someone from a different time zone makes changes to that sheet. Sheets adopt the time zone of the last person to access that sheet; simply viewing the sheet is enough to change the time zone.
Time zones and system columns
System Columns always use UTC in the back-end while the display value matches the time zone of the last person to access the sheet. This means that although the display value is in the sheet-viewers time zone, use of formulas and possibly API calls using System Column data may be returned based on the UTC time zone
Pacific Time overrides
When changes are made to a sheet via automation, cell links, or cross sheet formulas, the whole sheet is converted to Pacific Time because these services are hosted by service users with a Pacific Time setting. This means that TODAY() formulas and display system column display values may get updated if the customer is in a different time zone.