In the event of a tariff change or modification, unused tickets that have not been validated, such as single tickets, day passes or parts of the 4-pass ticket, can still be used 6 months after the fare change. Tickets that have to be validated, and tickets where the price has not changed, remain valid.
https://sbahn.berlin/en/tickets/the-...tariff-change/
(BVG and S-Bahn are part of the VBB that sets the prices for Berlin+Brandenburg region)