Part of my job is to put together a daily worldwide e-newsletter. So a few days before the start of a new month, I create a folder for that month that contains the blank word documents that will become the drafts of the newsletter. They all say the day of the week and date at the top, like this: Monday, April 2, 2012.

When I create them, the quickest way I’ve found to work is to take a previous month’s day (any day will do), and delete the irrelevant stuff, change the date, and re-save into the appropriate folder. Then, I go back into the doc and change the date but not the day, so I create all the Mondays for the month, then all the Tuesdays, and so on.

Here’s a delightful little oddity that I’ve discovered: the dates are oddly cyclical. The final Monday of the month links strangely to the first Tuesday; the final Tuesday links oddly to the first Wednesday, and so on. Occasionally the trend is broken (usually when the month has 31 days).

I’ll show you what I mean.

Taking April as an example, the last Monday in April is the 30. The first Tuesday in April is the 3. The last Tuesday in April is the 24th. The first Wednesday in April is the 4th. The final Wednesday in April is the 25th. The first Thursday is the 5th. The final Thursday in April is the 26th. The first Friday in April is the 6th. Obviously, once you see the pattern in the first day, it’s going to work out all week (barring a 31st month in which case one day won’t work), because the days number chronologically for the first week and the last week (as is to be expected). What’s interesting is that it works out nicely at all. Also, the last days of the month starts either 21 or 28 days after the first days (meaning, there is only one first Monday and only one last Monday) so the number is always advanced one “ones place” and two “tens places” or two less than 30 (that is, 30 + the original number – 2). Also, it’s a handy way of knowing what days of the week the end of the month works out to (in case you ever need to work it out in your head). If it’s Wednesday the 4th, you can think to yourself, “ok, the last Wednesday will be 4 + 30 – 2=32, doesn’t work, ok, it must be advance two tens, one one (25).” I don’t know why I imagine that’s easier to remember than any other system, but I like that there are these little rules.

Basically, I just like how it works out. I like making these blank documents to fill up later, because it gives me a little bit of joy to see it working out.