<lord of the rings meme>

one does not simply determine the current timezone

getTimeZoneOffset doesn't give you daylight savings, so the timezone might change between now and the time the event happens. new Date().toString() does seem to have a timezone code, but note that sometimes these are actually ambigious.

For example, India Standard Time

$ timedatectl set-timezone Asia/Kolkata
> new Date().toString()
'Wed Aug 22 2018 12:12:36 GMT+0530 (IST)'

and Ireland Summer Time

$ timedatectl set-timezone Europe/Dublin
> new Date().toString()
'Wed Aug 22 2018 07:42:52 GMT+0100 (IST)'

One time I missed a call because I was in Ireland but they thought I was in India.

Also, Australia also has EST/EDT, as does the US.

I guess you can look at the timezone name and the offset, that might work.