Calendar puzzle generator
The puzzle that sets itself a new challenge every morning: fit the pieces into the board so that only today's month and date stay uncovered. Size it to your printer, print it in two colours, and know before you start that every date has an answer.
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How it works
- 1
Pick an edition
Classic has at least 5 solutions for every date. Hard uses a different last piece and leaves some days with a single solution. The weekday edition adds a row of weekdays and a ninth piece, and the birthday edition puts a name on the board.
- 2
Size it to your printer
The cell size drives everything: 18 mm makes a board about 150 mm across, and anything from 12 mm to 26 mm works. The piece thickness and the clearance between piece and pocket are yours to set, so the fit suits your printer rather than ours.
- 3
Choose the colours
Bright, pastel or wood-tone pieces, and a board colour of your own. The months and dates can be printed as a flush inlay in a second colour — with a filament change at the right layer, or on a multi-material printer.
- 4
Download and print
The board and every piece come as separate STL or 3MF files, laid out for a 256 mm bed. All of it prints flat, with no supports.
Every date is proved, not hoped for
A calendar puzzle is only fun if today can be solved. A set of pieces that works for most dates and fails on the 29th of February is a very annoying object to own, and you would find out on the one day it matters.
So the piece sets here were found by search and then checked by a solver for every date: all 366 month-and-day pairs for the classic and hard editions, and all 2,604 month, date and weekday combinations for the weekday edition. They are our own piece sets rather than a copy of a commercial one.
- Classic
- Seven pentominoes and one six-cell piece. At least 5 solutions for every date, so a stuck morning always has somewhere to go.
- Hard
- The same seven pentominoes and a different six-cell piece. Some dates have exactly one solution.
- Weekday edition
- Nine pieces on a larger board: leave the month, the date and the day of the week uncovered.
- Birthday calendar
- A name on the board and a key card showing the one arrangement that leaves exactly their birthday open — a gift that says it was made for them.
Printing the puzzle
Print the board and the pieces flat. A 0.2 mm layer height, three or four perimeters and 15–20% infill suits almost everything here, and none of it needs supports when printed flat on the bed.
Clearance is the setting that decides whether the puzzle is pleasant. 0.3 mm suits most printers; go up to 0.4 mm if the pieces bind, or down if they rattle. The pieces are chamfered on top and bottom so they drop into the board without catching on a corner.
The labels are engraved into the board either way. For two colours, export with the inlay: it fills the engraving flush, so you can pause and swap filament where the labels start, or give the inlay its own colour on a multi-material printer.
Where it lives in the studio
The calendar puzzles are part of the Brain teasers in the Sets tab, next to the pentomino, Soma cube, sliding-block and number puzzles. Sets are included in the Pro and Ultra plans; you can open the studio and look at every edition before you decide.
Questions
Is every date really solvable?
Yes. The solver checked every one of the 366 dates for the classic and hard editions and all 2,604 combinations for the weekday edition before the piece sets were used.
How big is the finished puzzle?
With the default 18 mm cells the board is about 150 mm across. Smaller cells make a pocket-sized version; larger ones make a desk piece. Everything scales with the one number.
Can I print it in one colour?
Yes. Switch the second-colour labels off and the months and dates are engraved into the board instead of inlaid, which reads well in any single colour.
Can I make one as a gift?
The birthday edition takes a name of up to 18 letters and a date, prints the name on the board, and adds a key card with the arrangement that leaves exactly that date uncovered.
Related
Try it now
Pro includes this mode. Cookie cutters stay free.
Just one project? A 7-day Pro pass is €4.99, no subscription.