You should take a look at this question - it should have a lot of useful information for you in regards to your question about syncing time.
That said, think about how your application scales and work from there. A request per minute can easily add up to a load that isn't easy to handle.
Do you really need real-time syncing of time events if you're just going to have people schedule events at a future period of time/date? If this is for a calendar, you really just need to make sure that the client's time matches your at the hour and minute level, and that the dates are the same. After that, you can rely on the client's time, unless you're scheduling by the second. (Then again, I don't know what this calendar is for...)
Additionally, if you're saving their events server side, I'm not sure that it would do you any good to sync time in the way you're considering. If you're looking to push updates to all calendars at once when someone makes a change, you might look into alternative ways to do that.
Good luck - I hope this helps.