chipKIT Built-In Real Time Clock
The Microchip® PIC32MX320F128 based UNO32 features a native RTC system.
The chipKIT™ Uno32 reference manual provides all the details:
RTCC: Real Time Clock Calendar.
The PIC32 microcontroller contains an RTCC circuit that can be used to maintain time and date information.
The operation of the RTCC requires a 32.768Khz frequency source. Crystal X2 (not loaded), just above and to the right of the PIC32 microcontroller IC, is provided for you to solder a 32Khz watch crystal.
The Citizen CFS206-32.768KDZF-UB crystal can be used in this location.