# The pi day … aka The Feigenbaum constant day

Ok, so the pi-day is up and running (March 14, i.e., 3-14). At approximately half past three today, some kind of pi would be served around the globe.

In an older post I found some alternative pi days for those who don’t like the date-system (Month-Day):

and we found July 19 and July 22 as more “accurate” days for the pi – at least for us in Europe. The latter internationally acknowledged as the “Pi approximation day”. (Americans might claim March 1 as an approximation according to the principle Month/Day.)

So what else do we have? Is this it? Are there no other fancy constants that we could appreciate throughout the year?

Of course there is… forza some python and loop over the most commonly  (according to Wikipedia) used constants. Standard integers aside. A euro-date below is “Day/Month” and a US-date is a “Month/Day”. I have found the best-matching date in a least-square sense.

Notice the possible benefits of celebrating some/most constants twice a year if using both Euro and US date formats! I’ve however given preference to as early dates as possible for constants approximating to the same value for several dates. For example the interesting Legendre’s constant (= 1) which could be celebrated quite a few times throughout the year, but let’s stick to January 1.

It is also worth noticing  that the Feigenbaum constant approximation day could be celebrated today instead of pi.

• Btw – what else than celebrating the imaginary number i on February 30.
Euro US Value Constant
22/07 03/01 3.14159265359 The pi day
19/07 11/04 2.71828182846 Eulers day
17/12 07/05 1.41421356237 Pythagoras day
19/11 12/07 1.73205080757 Theodorus day
20/09 09/04 2.2360679775 sqrt5-day
04/07 11/19 0.577215664902 Euler-Mascheroni constant
13/08 08/05 1.61803398875 Golden ratio
03/11 06/23 0.261497212848 Meissel-Mertens constant
02/07 07/25 0.280169499024 Bernsteins constant
03/10 07/23 0.303663002899 Gauss-Kuzmin-Wirsing constant
04/11 06/17 0.353236371855 Hafner-Sarnak-McCurley constant
01/02 01/02 0.5 Landaus constant
04/07 04/07 0.56714329041 Omega constant
05/08 05/08 0.624329988544 Golomb-Dickman constant
07/11 09/14 0.6434105462 Cahens constant
02/03 02/03 0.660161815847 Twin prime constant
02/03 02/03 0.662743419349 Laplace limit
07/10 07/10 0.70258 Embree-Trefethen constant
07/09 10/13 0.764223653589 Landau-Ramanujan constant
09/11 09/11 0.8093940205 Alladi-Grinstead constant
07/08 07/08 0.87058838 Bruns constant for prime quadruplets
11/12 11/12 0.915965594177 Catalans constant
01/01 01/01 1 Legendres constant
11/10 11/10 1.0986858055 Lengyels constant
09/08 09/08 1.13198824 Viswanaths constant
06/05 06/05 1.20205690316 Aperys constant
13/10 09/07 1.30357726903 Conways constant
13/10 09/07 1.30637788386 Mills constant
04/03 04/03 1.32471795724 Plastic constant
16/11 10/07 1.45136923488 Ramanujan-Soldner constant
16/11 10/07 1.45607494858 Backhouses constant
16/11 03/02 1.4670780794 Porters constant
17/11 11/07 1.5396007178 Liebs squareice constant
08/05 08/05 1.60669515242 Erdos-Borwein constant
17/10 12/07 1.70521114011 Nivens constant
19/10 11/06 1.9021605831 Bruns constant for twin primes
23/10 07/03 2.29558714939 Universal parabolic constant
05/02 05/02 2.5029078751 Feigenbaum constant
31/12 08/03 2.58498175958 Sierpinskis constant
27/10 08/03 2.68545200107 Khinchins constant
14/05 11/04 2.80777024203 Fransen-Robinson constant
23/07 10/03 3.27582291872 Levys constant
27/08 10/03 3.35988566624 Reciprocal Fibonacci constant
14/03 09/02 4.6692016091 Feigenbaum constant
30/2 2/30 i, sqrt(-1) The imaginary day (30/2!)

## 3 thoughts on “The pi day … aka The Feigenbaum constant day”

• Cool, who could have imagined that! i didnt’t.

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