How far in advance should you send "hold the date" for anniversary party?

Question

Planning a 50th anniversary party. Location will involve overnight travel for many guests. How far in advance should I send "hold the date" notices?

Answer 1

I know for my grandparents we knew about the party about a year in advance. I don't believe we were formal enough to send notices, though. At least not for family.

I'd think the harder it is to find accommodations the earlier you'd want to warn people.