Working together with people over different time zones, time zone support is a critical feature for a calendar app. It doesn't suffice to agree on a time and time zone (e.g. 07:00 Taipei), and write down the time as represented on my machine in the Berlin time zone. Two things can happen:
Summer time shifts that I did not take into consideration. Summer time shifts can even happen at different days of the year for different countries, making it impossible to calculate the correct time in my Berlin time zone manually.
Changes of time zones: Time zones are political, and they might change in the future without us knowing yet. Therefore, a time needs to be bound to a specific time zone (city). It should be calculated back to my time zone and other people's time zones whenever the user looks up the calendar.
I am interested in helping with the implementation. I have experience with time zone management, but not much with Javascript programming though.