Typically found on wedding invitations, a save the date card is sent approximately 2-4 months prior to the actual invitation as a reminder to “reserve this date” for the event and not to schedule anything else on the said date. It’s done to avoid any scheduling conflicts, period. The excuses of “I had something else planned” simply won’t fly.
But, there are those who believe a save the date is the same as an rsvp. That’s not the case.
For a non-wedding event, a save the date isn’t required. In fact, sending one is a waste of time since no one will be planning an event so extravagant (save for an award show that everyone knows happens around the same time each year) you need to know about it several months in advance. This is especially true for a preview. No preview requires a save the date. Simply sending an invite 2-3 weeks before the event (with an rsvp email address or phone number) is more than enough.
And if the guest can’t attend, there’s always a follow up via email. Unless, it’s the Academy Awards; they will mail the absentee winner his/her Oscar.