The chip DS3231 was replaced on all new versions by the DS1307.
For which reason do you use now the DS1307 ?
Do you know if the last firmware 2.1.4 is compatible with the DS3231 ?
Because the big advantage of the DS3231 is no needed external crystal and ‘less’ current for the battery (100nA instead 500nA)
DS3231 and DS1307 are functionally the same, except that DS3231 has a built-in temperature compensated crystal, which makes it more accurate, but also the chip is much larger. They both use the same I2C address and libraries that work for DS1307 should work for DS3231 too.
Thanks for your feedback and clarification.
I was not sure that the firmware use the internal ram of the DS1307, not present in the DS3231.
My idea is to use the DS3231MZ with less pins than the DS3231SN.