V--I don't know what DL flight privs OP has w/DGS. The good part of a flight day now w/Delta is the 24 hr definition that has nothing to do with datelines.
I used to have companion privs and had limited number TOs which meant TransPac and TransAt. However, once used, I could fly to Central America/Carib/Mex--go figger! When I used my TOs (mostly RT EU) I had to chose those destinations in what DL called "system flights". That was pre-NW and certainly has changed, but so has my status as spouse!