But you're just converting one time to another. If you know their reported UTC time and their reported offset to local, isn't that all you need? For greater pre

But you're just converting one time to another. If you know their reported UTC time and their reported offset to local, isn't that all you need? For greater precision, ask for their geolocation or use an IP address to narrow down the possibilities, though offset obvious helps. Now that I think about it, you could auto-suggest based on offset and embed a list of locations per option if they needed to pick between daylight savings or not, for instance. There's room for an interesting widget or service, but it would need to be updated almost as much as a US sales tax calculation widget ;-)