What timezone does the API return data in?

Hi,

I am using the metric export API and I was wondering what timezone the data is in.
https://developers.klaviyo.com/en/reference/metric-export

I understand that the reports in the UI are formatted according to the organisations timezone setting but what about data out of the API?
I am assuming that all dates in the API are a set timezone and there is no way to manipulate this?  Is it UTC?

If I set the start_date and end_date in the API call in the response it comes back with no time allocations.  Is the end date inclusive of the whole day
Example:
&unit=day&start_date=2022-05-01&end_date=2022-05-02
The response returns
"start_date": "2022-05-01 00:00:00",
"end_date": "2022-05-02 00:00:00",

I assume the data returned is the end_date up to "2022-05-02 23:59:59" ?

Changing the unit to hour doesn’t return time stamps with a timezone so it isn’t obvious what timezone those hour metrics are.
 

Thanks