Fix 'out of range' issue, add mode

[JoelGodin]

Hi, I fixed the out-of-range issue and added a mode 2 (US Month, Day, Year, 12hr clock, am/pm.

[qbnut]

I was going to raise the PR to resolve the 8th day-of-the-week issue (#7), only to find somebody already had, but the PR is from nearly a year ago!

Of course, I've fixed my local version of the code, but it'd be great to get this change back into main for future users