Our system will automatically default to every transaction being on a UTC time setting as this is what many exchanges also do.
UTC (universal time code) is simply the time in London (Greenwich Mean Time) and is just a way that everyone in the world can talk about the time right now.
Your time zone may matter at the start and end of the year.
If you made trades on Dec 31st to tax loss harvest but our system is showing those trades happening on Jan 1 because of time zone effects, that would be a reason to change your time settings from UTC to local time.
If you would like to change the time zone for your tax calculations to your current time zone, simply go to the Gear Icon on the top right, then click Account Settings.
Then click "Set Time Zone" on the left and select your local time zone.