Timing
Sevas happen when the place performs them, not when it would be convenient for us to say they happened.
The correct time
An archana happens during the temple's archana. Fajr happens at Fajr. A mass intention is offered at a mass. Where a seva has a proper hour, that hour decides the schedule, and it may mean tomorrow morning rather than this afternoon.
What same-day means
Where the place's schedule allows it, most sevas requested before mid-morning IST are performed the same day and the proof arrives the same evening. Where the schedule does not allow it, the earliest honest date is shown before you pay.
Muhurats and auspicious days
If your family follows a specific tithi or muhurat, you can set it. The seva is then performed on that date and not before, even if a Sevak is free earlier.
Time zones
Everything is scheduled in IST, because that is where the seva happens, and shown to you in your own time zone as well. Your proof carries IST, so the record matches the place.
Festival days run long. On Diwali or Eid your proof may arrive late at night IST. It will arrive.