Since I live in Europe, we have daylight saving time and standard time. The clocks are mostly synchronized by the longwave time signal DCF77. Since we use the high-precision RTC DS3231 and a microcontroller, this is not necessary. For daylight saving time, the time change takes place on the last Sunday in March. Thereby at 2:00 a.m., the clock is advanced by one hour. For the winter time (standard time) the time change takes place on the last Sunday in October. At 3:00 a.m. the clock is set back by one hour.