date_modified range doesn't match with changed date

[joss...@bemyapp.com]

Hi !
I use the eventbrite API to gather events in a certain range with a certain query.
Here is my query (set your own token ;) ):
https://www.eventbriteapi.com/v3/events/search/?q=hackathon&date_modified.range_start=2017-11-14T09%3A00%3A34Z&date_modified.range_end=2017-11-14T13%3A00%3A30Z&token=[YOUR-TOKEN]

The range is from 2017-11-14T09:00:34Z to 2017-11-14T13:00:30Z

In this example, the first result I get is "Hack The City - Hackathon" which modified date is 2017-11-14T21:48:20Z.

Did I misunderstood something on this query ?

Thank you !