libical seems to only accept the Olsen city name to look up timezones in its database. What I've got that's portable is a struct tm which has a GMT offset and the shorthand 3-4 letter code (EST/EDT etc) but there's no function that accepts that in libical.
I have a really lousy way where I scan the tz list from libical trying to match the tznames, and that will probably work, but I am well aware this is a bad idea. But I haven't found any other way of getting the local timezone into a libical icaltimetype.
Am I missing something simple?
And by portable I mean windows, osx and linux.
This is a c program I'm writing. But I see now that tz offset is not posix, so that won't do.