I recently subscribed to an email for an expiring domains search at Snapnames. In it the deadlines to backorder the names are shown. Some names have a deadline of 12.15 and others 21.00 - they are all dot com. The 12.15 deadline is in line with what I thought, and also corresponds to the daily drop time.
But where does the 21.00 deadline come from?

I think dot-org pending deletes have different times.

The dates given for many exclusive domains at snap may differ by a long way from the actual drop date - even months.

I remember asking snap about this. There are two types of auction format.

1) You add the name - immediately there is an auction with the clock ticking.

2) You add the name - no immediate auction. Three day auction starts on the "drop" date.

I think a lot of it is just what they think will work best. Could be wrong about this, haven't been on snap for a while.

The names are definitely expiring (ie not just auction sales), and both Namejet and Pool also show them as expiring on the same day.
Maybe they are with a registrar with whom Snapnames has an agreement, and for this reason they drop later than usual?