I'm curious, when would you use this?
As far as I can recall, the only time I need to know day-of-month is when scheduling and I need my actual calendar with existing appointments for that.
As far as I can recall, the only time I need to know day-of-month is when scheduling and I need my actual calendar with existing appointments for that.
Or to check where Christmas falls or something like that.
Ultimately it's a little thing to keep in your wallet. Not something to replace an appointment diary.
https://en.wikipedia.org/wiki/Doomsday_rule
I learned this years ago and it is life changing. It can be used to figure out the day of the week of any day in a couple seconds.
For example, the rule immediately tells me that Boxing Day is a Tuesday[0], so I know Christmas falls on a Monday this year.
[0] as does 3/14, 4/4, 5/9, 6/6, 7/4, 7/11, 8/8, 9/5, 10/10, 10/31, 11/7, and 12/12 since those anchor points are always on the same “doomsday”. Based on that, any day is just a little bit of addition/subtraction.