RTC drift adjustment and calibration

Hi there.
I'm using STM32F103 and external 32.768kHz crystal in LSE Mode, but I've seen drifting about 10sec per day, so I wonder how can I calibrate this drift.
Also in the `RTC_setPrediv(int8_t asynch, int16_t synch)` there no definition for STM32F1xx.
I found one library which said did something about it: https://github.com/ag88/stm32duino_rtcadj
but it works with maple core.