Hi whitebuck. Welcome to Method!
Dates are stored in Method in UTC time (https://en.wikipedia.org/wiki/Coordinated_Universal_Time).
The UI converts the UTC time to your local time when displaying, and converts local time to UTC when saving. That way the time is accurate to the viewer regardless of where they are around the world.
So, when using the API you'll have to convert your local time to UTC time before saving.
Hope that helps,
Paul