friendiversary

 friendiversary  is the anniversary of when you became friends with someone, a feature supported by some silos like Facebook as part of their on this day support.

Why
If you post when you meet someone (e.g. "Nice to meet you URL/@-name") then your publishing software could remind you a year later, prompting you to message them.

How
In the past some bloggers would post XFN "met" posts linking to people they meet.

Today there is no (new) publishing/format convention(s) for such "met" posts, so you may have to develop one for yourself, e.g. try looking at your own organic "met" posts to see if you can discern a pattern, and write software to remind you in the future.

IndieWeb Examples
None so far.

Facebook
Facebook shows friendiversaries with "You became friends on Facebook with ..." as part of their on this day feature.