25 Dec 2019 21 Dec 2019 22 Jan 2020
This is actually easy. You need to complete all 93 challenges for a whole month.
There are always 3 puzzles and always the same ones. A classic game, an irregular game and an ice breaking challenge on various difficulties.
Based on the month it can either be 87 in February, 90 on 30-day-month or 93 on 31-day-months.
The challenges are actually easy - if you encounter some problems, just restart and there will be a new random game. I did this for this month so far and it took me about 2 hours to complete all the games back from 1st to 21th December.
EDIT: As of today 22.1.2020 this seems still be glitched. You're completed challenges and the counter may not be the same, which means you can get this achievement even before the month ends.
Always check your progress!