German law normally requires the creditor to send a reminder before the debtor is formally in default. But where the parties have fixed a performance date by the calendar, no reminder is required at all — § 286 Abs. 2 Nr. 1 BGB. Default begins the moment the date passes.
The Latin maxim is quoted in German textbooks: dies interpellat pro homine — the day admonishes in place of the man.
A German who agreed a date does not expect to be chased, and the law agrees with him.