The optimal arrival time accounts for several different, sometimes competing considerations: If you’re the first one there, it can be a little awkward.

If you show up long after everyone else, you might miss the best parts or risk rudeness.

• Most likely, you want to arrive just as the party’s gaining real momentum, a Goldilocks window of time that’s neither early nor late.
• For low-key parties with friends and food, the ideal time to show up can be 38 minutes after the start time.
• 30 minutes would be too early, and 45 minutes too late!

Part of it has to do with a fundamental tension between what's called "clock time" and "event time"

• Clock Time: The specific time on the watch.
• Event time: a more fluid framework that follows our social rhythms