Date Formatting

Dates are formatted as milliseconds since the Unix epoch (January 1, 1970) returned as an integer OR in a string.
Looks at specific API docs to see what format is required.
More information In JavaScript Date Object MDN

Timezones

Our API always returns timestamps in UTC (Coordinated Universal Time).

The start date and due date on tasks that don't have a start or due time will default to 4 am in the local time zone of the user who added the start or due date.

If that user changes their timezone later, task start dates and due dates will not be retroactively updated.