There isn't an official builder (think a user once said he'd contribute one, but it hasn't made it to production). But I slapped this together today and it should help:
Coupla screenshots:
Click the "Set in current time zone..." button and datetimes you choose are assumed to be in your local timezone. (Then they get converted to UTC/Z for the generated URL, but you don't need to worry about that, just copy and paste.)
This simple builder doesn't support timezones other than UTC and your machine's current tz. Juggling timezones is much harder than most people think (as I've mentioned a lot in the context of Velocity scripts, where people constantly mess it up). In browsers, you can't do accurate timezone stuff without a 3rd-party library -- the de facto standard being moment.js -- as past and future boundaries for non-local timezones are just not available. It would be possible to use moment.js to create a great tz-aware builder, I just haven't had the time. 
Just slapped together huh! Much more than I can do Sandy Thanks so much!!! TZ's are a pain in the !$$--don't even want to go the Velocity route for this project.
This is lovely, and would be even lovelier if I could access the URL since our network security is so tight.
Gerard Donnelly -hey can you access the link Sanford shared for the Agical date/range builder? Tried in Incognito....no dice, but you're on a different server so maybe you'll have better luck 
.png)