Уходили на пару секунд в сутки. Решилось качественным кварцем GEYER KX-38 32.768 6pF (6 pF для ds1302, для 1307 - 12.5pF) Рекомендации по кварцу в даташите. X1, X2 - Connections for a standard 32.768 kHz quartz crystal. The internal oscillator circuitry is designed for operation with a crystal having a specified load capacitance (CL) of 12.5 pF. For more information on crystal selection and crystal layout considerations, please consult Application Note 58, “Crystal Considerations with Dallas Real Time Clocks.” The DS1307 can also be driven by an external 32.768 kHz oscillator. In this configuration, the X1 pin is connected to the external oscillator signal and the X2 pin is floated.