Keep track of days of the week

[ningrui-li]

Consider implementing some way to count the days of the weeks or maybe even the date. Main goal of this is to make sure that we only light up "Duke IEEE Time!" when it is Saturday (or whatever day we decide to meet on in the future).

Holding the date would allow us to maybe do a flashy animation on certain holidays. Or use a special color scheme if we get around to making a clock with NeoPixels.