As of now, while submitting an advance reservation, PBS does not check for the timezone as it does for a standing reservation. It is a possibility that an advance reservation can be submitted to start after a very long time, say 7 months from now. In such a case, the start time can be affected by DST adjustments that fall in between current time and the start of the reservation. So, setting the PBS_TZID should be mandatory for advance reservations as well.
For a better understanding of this requirement, read the discussion here.
1. Advance reservations should be tied with a timezone just like the standing reservations.
2. Accounting should have information about the timezone associated with the reservation.