Ask HN: Programmer-friendly time zone conversion tool?

Hi there. I am looking for a tool that will convert dates/times from logs on other servers to other time zones (predominantly UTC) so I can marry up log entries etc.

The major sites that convert times that I found on Google require you to fill in a form with multiple drop downs etc. which seems silly when I have the time string on my clipboard, and I am going to want to repeat the operation many times quickly.

Is there a nice tool online or chrome extension etc. that does a good job of this?

If not I might have to scratch my own itch here and build something.