Glossary

UID (event identifier)

The stable identifier that lets calendar apps recognize an updated event as the same event.

Every iCalendar event carries a UID. When a feed publishes an event again with the same UID and a higher sequence number, subscribing apps update the existing entry instead of duplicating it.

Feeds that regenerate UIDs on every publish cause the classic symptom: subscribers see the same practice twice, then three times. Stable UIDs are what make edit once, update everywhere actually work.