Hi,
My understanding on this requirement is that you need I2C code to write/read RTC registers using C. I2C controller is available on PIC Microcontroller.
I have over eight years of experience in writing, debugging software for embedded devices such as 8-Bit, 16-Bit and 32-Bit Controllers and Processors.
I have extensively worked on I2C. We have interfaced RTC via I2C.