When is it OK to talk about Bodyguard?
Life used to be easy. Four channels, no streaming and barely any videotape. Everyone watched the same thing on a Sunday and the ones who didn't were never going to see it.
So you could go into to work on Monday and talk freely about who shot Mr Burns in The Simpsons or who actually did frame Roger Rabbit.
Then for a few years, everyone was streaming. Spoilers didn't come up because no one was watching the same thing.
What do we talk about when you're on season five of Breaking Bad and I'm on season two of Lost?
But the massive ratings for Love Island and Bodyguard have ushered in the new era of timeshifting. Almost everyone's watching big event television - but some people are watching it later than others.
So how long should you wait before discussing what happened to David Budd and Julia Montague?
We took a look at the streaming figures for users who are signed in to iPlayer.
For the season finales of five other major shows on the platform, we asked how long before almost everyone has streamed it (of those who ever will).
The rules are different for different genres. For dramas like Doctor Foster, Doctor Who or Line of Duty, it took almost two weeks before 90% of iPlayer streamers had watched the show.
But Bake Off and Strictly reached that point within four days. Just knowing the winner can spoil a grand finale, so you need to watch quickly. For dramas, the final reveal is a bit more complicated. And in Doctor Foster, there were no winners.
That suggests you should wait a fortnight before you start any "kompromat" chat on the train.
But streamers only account for some of the viewers. We didn't look at set-top recording or include the overnight viewing figures in our analysis.
- Bodyguard most watched BBC drama in 10 years
- Unanswered questions from the final episode of Bodyguard
- Bodyguard’s David Budd could be about to save more lives
Catch-up is growing fast, but most people still watch event TV on the night.
If you're feeling impatient, you could start when 50% of streamers have watched the show.
For these dramas, and for these competitions, that's a wait of only one day. Your chances of spoiling someone's fun should be pretty low by then.
But before you start waving our chart in front of "whiny spoiler babies", there's one last thing you need to bear in mind.
There are some people you really don't want to annoy, even if they are in a tiny minority.
If your boss is part of that last 50% or 10% or even 1% of streamers, you might want to wait an extra week before you tweet. Just in case.
Research and analysis by Maryam Ahmed and Joshua Feldman.