The current code interprets the 'century' flag as the year 2100. However the
DS3231 hardware does not incorporate this flag in its leap year calculation, so
will incorrectly consider the year 2100 as a leap year and increment from
2100-02-28 to 2100-02-29 instead of the correct 2100-03-01.
The 'century' bit is not useful for anything as far as I can tell. But instead
of removing the code that uses the 'century' bit, I thought it would be less
intrusive to just document the current behavior.
I also verified my interpretation of the DS3231 datasheet and my implementation
of this formula by placing a DS3231 chip in the freezer section of my
refrigerator for an hour or two, then reading the temperature. I got -16C,
which is close enough to the -18C that the freezer was set to.
soypat
Brian Park
deadprogram
Daniel Esteban