Were those recurring meetings or one-offs?

Part of a product I'm working on now is being able to schedule repeating tasks every day, every month, etc. Which means that "07:30 every Friday" has to happen at 07:30 in the author's timezone, whether or not DST is active. To my knowledge Javascript can only tell you the timezone offset from UTC for a given date/time. You can determine the DST-less offset that way, but there are multiple timezones sharing the same offset (e.g. PHP has 63 separate timezone records for Europe alone) and then simply matching them by offsets doesn't work ideally, you need the user to make a choice.