+1. i think the only time you need to store timezones is when you don't have an absolute point in time. say you are storing a time without a date. ie: 5:00pm. you need a timezone associated with that time somehow.
Yes. When you schedule a recurring event, such as daily reminder, you will have to store timezone. In that case, you are storing a scheduling specification, not a real date/time. You don't have the complete information, such as year/month, etc.