By default, the API accepts and returns times in the timezone set in the user's profile. If there is no timezone set, it defaults to UTC. If the request is made without any user context, it defaults to UTC.
The best way to handle dates and times properly is to include a "Timezone" HTTP header in your requests. Sending a header like the following will cause your input to be parsed in the timezone specified in the header, and any times output by the API will also be in your timezone.
Any date value in the API can accept a Unix timestamp, or a date formatted according to the ISO-8601 standard. The most common format for sending datestamps to the API should be "YYYY-mm-ddThh:mm:ss+tzoffset", such as "2011-03-26T15:36:00-07:00".
Many methods have a similar format for handling dates and times, there is often a
time_to. The date pair exists to set the absolute start and end date/time for the item. The time pair exists to specify recurring times for the item.
For example, when creating a place, you can specify start and end date.