Wikipedia:Reference desk/Archives/Mathematics/2019 September 14

= September 14 =

Fibonacci numbers and Friday the 13th
Yesterday was a Friday the 13th. But there is also an interesting coincidence with Fibonacci numbers that will occur in 2021. Namely, August 13, 2021, which happens to be a Friday the 13th, could also be written (in the United States) as 8/13/21, which consists of three consecutive Fibonacci numbers.

Does anyone think that we will have a Fibonacci numbers celebration on August 13, 2021 (e.g. a cake with the Fibonacci sequence on it)?

In the Julian calendar, August 13 was on a Friday in AD 521, 1221, and (in Greece) 1921. In the Gregorian calendar, August 13 was on a Friday in 1621. Of course, because the Gregorian calendar repeats every four centuries, August 13 will also be on a Friday in 2421 and 2821. GeoffreyT2000 (talk) 14:48, 14 September 2019 (UTC)
 * We could call it phi-day the 13th :) Much of the world would write it as 13/8/21, not quite as compelling, but already there's 3/14 as pi day and even 6/28 as tau day. --RDBury (talk) 17:46, 14 September 2019 (UTC)
 * November 23 is Fibonacci Day. An article was deleted as an alleged hoax. I'm not sure it's worth an article but finds many sources. I guess 01:12:35 on 8/13/21 will get some attention at the time. PrimeHunter (talk)
 * You forgot that Friday, as the 5th day of week is also part of the Fibonacci sequence ;) 93.136.115.136 (talk) 08:17, 15 September 2019 (UTC)

Maybe we need an American Wikipedia just for people who write dates illogically. It took too much of my brain power to keep translating that strange notation used by only 5% of the world's population. Will the US keep that silliness up forever? HiLo48 (talk) 02:29, 15 September 2019 (UTC)
 * Please avoid arguing personal prejudices here. "8/13/21" is a perfectly logical way to abbreviate "August 13, '21" since it keeps the components in the same order.  Other notations such as the international standard 2021-08-13 are logical for other reasons. --76.69.116.4 (talk) 05:56, 15 September 2019 (UTC)
 * My personal preference is for simplicity and logic. Neither of the American usages you illustrated display those characteristics. HiLo48 (talk) 07:02, 15 September 2019 (UTC)
 * (1) If you push the argument that the US usage is absurd because the items are not ordered, you will find that 2021-08-13 12:34 is more logical than 13-08-2021 12:34. (I do think the US usage is absurd, but the dd-mm-yyyy is only slightly less so.) (2) Decimal time is simple and logic. I doubt you use it. Tigraan Click here to contact me 09:21, 19 September 2019 (UTC)

The original query is asking for a prediction and I'm afraid that is also off-topic here. --76.69.116.4 (talk) 05:56, 15 September 2019 (UTC)
 * Couldn't some genius work out the probability of such an event occurring? --   Jack of Oz   [pleasantries]  23:48, 18 September 2019 (UTC)


 * Will we have a celebration, with cake? Well yes, if chooses to organise it. {The poster formerly known as 87.81.230.195} 90.202.210.107 (talk) 12:23, 19 September 2019 (UTC)