Microchip's real-time clocks are highly integrated with non-volatile memory and cost effective features for real life applications. This includes a battery switchover with timestamp to maintain timekeeping in order to log the time and duration of any power failure. When higher accuracy is necessary, digital trimming compensates for crystal frequencies that drift over temperature.
The MCP795Wxx series are accurate real-time clock devices that use an external 32.768 KHz crystal as a timing source. Most RTCCs use a crystal for timing with the understanding that all crystals drift in frequency over temperature.