How is an RTC (Real-Time Clock) used in embedded systems?

RTC maintains accurate time even when the main system is powered off, using a dedicated low-power oscillator (usually 32.768 kHz crystal) and backup battery. Features: Independent time counting (seconds, minutes, hours, date). Alarm interrupts for scheduled wake-up. Calendar with leap year handling. Low power consumption (few microamps). Backup domain survives main power loss. Applications: Timestamping sensor data and logs. Scheduled operations (data upload, measurements). Power management (wake at specific times). Data logging with accurate time reference. User-facing time display. Implementation considerations: Initial time setting (manual, NTP, GPS). Drift compensation (ppm adjustment). Handling daylight saving time. Backup battery monitoring. Calendar rollover handling. Common interfaces: Internal MCU peripheral, external I2C chips (DS3231, PCF8563).