Stripe assigns cohorts to subscribers based on when they first started generating positive Monthly Recurring Revenue (MRR) by starting active paying subscriptions.

For all subscribers in a cohort, we measure retention by checking to see whether a subscriber churned during a given month, based on Coordinated Universal Time (UTC). Retention is the percentage of subscribers from that cohort who haven't yet churned by the end of the month.

After a subscriber churns, if they re-subscribe, they will remain part of their original cohort.