How it all started

In The Netherlands 67 is currently the retirement age. For me this happened in 2025 on

Jan	Feb	Mar	Apr	May	Jun	xxx
Jul	Aug	Sep	Oct	Nov	Dec	xxx
1	2	3	4	5	6	7
8	9	10	11	12	13	14
15	16	17	18	19	20	21
22	23	24	25	26	27	28
29	30	31	xxx	xxx	xxx	xxx

My farewell party at the company was already a week before on

Jan	Feb	Mar	Apr	May	Jun	xxx
Jul	Aug	Sep	Oct	Nov	Dec	xxx
1	2	3	4	5	6	7
8	9	10	11	12	13	14
15	16	17	18	19	20	21
22	23	24	25	26	27	28
29	30	31	xxx	xxx	xxx	xxx

On that occasion my colleague Alex gave me A-Puzzle-A-Day.
At first glance I thought: "This is not for me, but I can automate this without much difficulty".

I was wrong twice: while trying to create a program I got interested in the puzzle and found some dates offline; not necessarily the current calendar date, but at least all pieces fitted somewhere leaving 2 squares open.

My first programming attempt turned out to be very slow. Naïvely I expected to calculate all possibilities using JavaScript within HTML. In short: just another page in my personal calculation Blogspot. As you are now reading this separate Blogspot, you understand this did not work out.