Is there any way to access the date in UTC (or the UNIX/epoch/time_t time (seconds since Jan 1 1970))
from a script?

Also: can I define a scheduler which triggers on a UTC time rather than the local time?
(yes I know i coudl just run the script hourly and then in it test the date, but that seems wasteful)

How about:
Regarding scheduler, it's local time based. You could setup your router with UTC time as a work-around...