DS3231 clock, time on battery

[awneil]

Indeed.

There was a post on here only the other day where someone had checked signal at the source (where it was fine) but there was a fault meaning it wasn't actually reaching the input pin.

EDIT - Found it:

How to check if value has changed in void loop?

Indeed - and remember that not all problems are software problems. Also check at the input pin to the ADC - to confirm that the signal is actually getting to it. As @Grumpy_Mike said, solderless breadboards are notorious for poor connections.