Examples' pictures:

STM32F103C8 Blackpill ( PB12)

1. Serialport set and display RTC clock. based on https://github.com/rogerclarkmelbourne/Arduino_STM32

   . 1st step change to your timezone in the sketch; . next step get Unix epoch time from https://www.epochconverter.com/ ; . last step input the 10 bits number( example: 1503945555) to Serialport ; . the clock will be reset to you wanted; . use timelib library.

2. Use new RTClock library of STM32F103, add Weekday. Others same function as 1.