A trivial tool to help me convert times to UTC and back.
go install github.com/joeshaw/utc@latest
Times without a time zone are assumed to be in local time. The time zone abbreviations are not DST-aware. They assume the location on the current date, meaning that e.g. EST and EDT are equivalent and map to America/New_York.
Convert from local time to UTC:
$ utc 12:30
16:30 UTC
Convert from a specific US time zone to UTC:
$ utc 12:30 pdt
19:30 UTC
Convert from a UTC time to local time:
$ utc -l 16:30 utc
12:30 EDT
Convert from a specific US time zone to local time:
$ utc -l 12:30 pdt
15:30 EDT