I didn't understand how the first test is supposed to return 6 and the last, -1.

I'm trying this in Python 3.6, if anyone can point sources helpful to acccomplish this task, I'd greatly appreciate.

Would you mind looking at my code and perhaps giving me a direction? Any help would be appreciated.

Thanks, will look for alternatives.

We should take into account that the Gregorian Calendar began on a Saturday, correct?