Your usage is calculated from the time you start your trip until it ends.
However, please note that the daily usage allowance consumption is finalised at the date/time that you end your trip, not from the date/time you start your trip. For example:
You start a trip at 10:00 AM and end it at 11:00 AM, but your Pass expired at 10:30 AM. The trip will then be fully charged at the standard rate instead of being partially covered by the Pass that expired during the trip.