This page is dedicated to dates that are also valid siteswap juggling patterns when printed in ISO 8601 format (YYYYMMDD).

This is 20241124, the first one that happened after I started investigating this idea: Not very challenging, but it amuses me. (instagram video)

The original inspiration for this is the tradition among jugglers of celebrating 423 Day (April 23rd, commonly written in North American as 4-23) by juggling siteswap pattern 423. It's basically the same idea as eating pie on March 14.

The way dates are usually written in the US (MM/DD/YYYY) is terrible. Why would you put the least significant part in the middle? The more common way outside the US (DD/MM/YYYY) is a bit better because at least the parts are sorted from least to most significant, but is easily confused with the US way. The ISO 8601 format (YYYY-MM-DD) is unambiguous (I'm pretty sure most people can understand 2024-08-09 even if they've never seen this format before) and also allows computers to sort them without any special handling (if, say, you have several files with dates in their names).

Also ISO 8601 is a standard.

The dashes are optional.

(If you're American and can't get over the habit of putting the month first, that's ok, because siteswaps are cyclic, so MMDDYYYY is really the same as YYYYMMDD. If you're from anywhere else, this doesn't help you.)

Most of the valid siteswap dates in the next 10 years are 2-ball patterns, so maybe not all that interesting. The next 3-ball pattern (as of this writing in 2024) is 20281119, but it has those unfortunate 8-beat and 9-beat throws that will make it rather challenging. There's a 3-ball pattern with a highest throw of 7 on 20340627, still pretty hard. Unfortunately there are no 3-ball patterns with maximum throws of 5 or less in the next 400 years. This is 24530424:

This spreadsheet shows the next 5000 valid siteswap dates. Each one includes two links to animations of the pattern (Gunswap, which powers the 3D animations shown above, and Juggling Lab, which gives you a downloadable GIF). The code is here.