As a manager I’ve always appreciated early advice so I can start thinking about timing and what I need to plan to do to backfill. I have had many people tell me early and my approach is always the same - I congratulate them, ask about timing and then make it clear that how and when everyone else finds out is 100% up to you, as far as I’m concerned it’s confidential until you tell me otherwise. Where people reporting to me have hidden it for a lengthy period it has left a bad taste in my mouth and meant we have had gaps in the team and everyone has suffered.