3D Printed Perpetual Calendar Clock Ver. 2

A Clock with a Perpetual Calendar Mechanism

This clock features a perpetual calendar mechanism that correctly handles all month lengths, including February in leap years. Despite the limited torque of a standard quartz clock movement, a simple yet ingenious mechanical design enables this complex function.

Numerous improvements have been made over Version 1. The drive gear train from the hour hand to the main cam is now concealed behind the front panel—not only for aesthetic reasons, but also to minimize the gap between the clock hands and the index markings.

Features:

1. The calendar advances automatically, requiring no manual adjustment until March 2100.
2. Powered by a commercially available battery-operated quartz movement, it runs for extended periods without an external power supply.
3. The calendar can be easily adjusted by manually rotating the clock hands.
4. The flat rear surface allows the clock to hang neatly and flush against a wall.
5. A skeleton design reveals the internal mechanism, making assembly straightforward and visually engaging.
6. No screw heads are visible from the front, contributing to a clean appearance.
7. All parts are designed for easy 3D printing without the need for support structures.
8. A visually appealing finish is achieved using multi-material 3D printing.
9. The calendar sub-dial hands (day, month, day of the week, and 24-hour) are aligned in height with the front panel, preventing any visual offset when viewed from an angle.
10. The main clock hands (hour, minute, and second) are also positioned close to the front panel, and the standard hands that come with the movement can now be used.

Some parts are carried over from ver.1, but the assembly process is completely different. Therefore I upload this clock model as an independent instructables.

Apr 22nd, 2025 : Models for small printers (210 x 210mm build plate) and minimum version (200 x 200mm) are added. See Step 9.

1. Battery-powered quartz clock movement commonly sold in online stores such as amazon.com. I used this one. The length of the hour axis should be 12mm or more.
2. An assortment of 2mm tapping screws. It is also sold in online stores such as Amazon or AliExpress. This clock uses relatively short tapping screws.
3. A M8 nut made of steel.

1. disassemble the movement and shorten the thread using hacksaw. Ideal length of the thread (measured from the top surface of the clock body, not from the protrusion around the thread) is around 4mm, because the thread to mount the movement to the clock face is usually too long.
2. Shave the shaft for the hour hand to form two flat sides. It is necessary to engage the gear to the shaft securely .
3. Make sure that the clock movement properly works after reassemble.

Print front face panel using multiple colors.

If you have multi-material system such as Prusa MMU or Bambu Lab AMS

1. Load four files (face.stl, face-dial.stl, face-letter.stl, face-index.stl) as a single assembled model.
2. Give different colors for certain parts.

If you do not have multi-material system

1. Load three files (face.stl, face-dial.stl, face-index.stl) as a single assembled model. Do not use face-letter.stl.
2. Change the filament during print. After printing two or three layers, pause the printer, change the filament to the different color, then resume the print.

1. Print the parts with supplied posture. No support structure needed.
2. Remove blob and debris on gears carefully. It is very important to make the clock driven by very weak torque.

Please take a look at the assembly guide video above.

1. Attach "date-month-idler1.stl" and "date-month-ider2.stl" using "date-month-idler-retainer.stl" by using three screws.
2. Attach "month-spring.stl", "date-spring.stl" and "week-spring.stl" by a screw for each.
3. Attach "week-drive-gear.stl" by a screw. Not too tight, it should rotate smoothly.

1. Attach the clock movement to the internal frame.
2. Set "hour-gear.stl" to the hour axis of the movement.
3. Place the "hour-idle-gear.stl" to the axis behind the front panel, then attach the internal frame to the front panel with 5 screws.
4. Attach "month-hand.stl" and "month-gear.stl" to the frame. You do not need to care about the direction of the gear.
5. Attach "week-hand.stl" and "week-driven-gear.stl" to the frame. A notch on the "week-driven-gear.stl" should be aligned to the week-hand.
6. Attach "date-hand.stl" and "date-rotor.stl" to the frame. A protrusion of the date-rotor.stl should be close to the date-hand.
7. Stick steel M8 nut to the hole of "main-arm-a.stl" as a weight.
8. Attach "main-arm-b.stl" to "main-arm-a.stl" by using a short screw. It should rotate smoothly. If it is not smooth, enlarge the hole of "main-arm-b.stl" by 2.5mm drill. Please use short screw for it.
9. Attach main-arm assembly to the frame.
10. Attach "24h-hand.stl", "24h-gear.stl" and "24h-cam.stl" to the frame. It is better to stick "24h-hand" and "24h-gear" in prior. The edge of the cam should be aligned to the hand.

1. Insert "program-wheel.stl" to the axis of internal frame. Align the relationship between the month hand and program wheel using February position.
2. Engage front and rear frame. Not to pinch three springs behind the gears.
3. Adjust the position of "week-drive-gear". The week hand should be rotated at midnight.
4. Fix two units by 8 screws.
5. Adjust the strength of three spring by release and tighten the screws.
6. Adjust the position of hands by using the small free play between gears and hands.
7. Attach clock hands (hour, minute and second).
8. Check that the calendar works properly.

1. The time is adjusted using the rear wheel of the clock movement—just like a typical wall-mounted analog clock.
2. The day-of-the-week hand can be manually rotated in either direction, except when the time is between 22:00 and 02:00. If you need to adjust it during this period, temporarily shift the time outside that range.
3. To rotate the month hand, raise the main arm through the opening on the left side of the clock, as the program wheel is normally locked by the main arm.
4. The date hand can only be rotated clockwise. When advancing from the 31st to the 1st, the month hand (program wheel) is also turned by the date hand, so the main arm must be raised as well.

If you give the clock to a friend, please attach a printed copy of operation-manual.pdf below.

Non-English face plates for this clock.

Please note that this is not for the older versions such as

1. Quartz-movement driven clock ver.1
2. Stepper-motor driven clock

Currently available languages

1. Spanish (two versions : MZO or MAR for March in English)
2. Catalan
3. Italian (two versions : GEN or DIC on top)
4. Danish
5. Portuguese
6. German
7. French
8. Ukrainian
9. Russian
10. Turkish
11. Traditional Japanese (two versions : 睦月 or 師走 on top)

Versions for other languages would be added on request.

I have not tested all variants. Please notify me if you find any problem.

The original model requires printers with 250 x 250mm build volume. The model here is for 210 x 210mm printers such as Prusa MK3S. Some gears and arms protrude from the body a bit.

1. Load the model to your slicer then rotate 45degrees around Z axis.
2. Use "face-small.stl" and "face-index-small.stl" with original "face-dial.stl" and "face-letter.stl". In other words,
3. Use "face-small.stl" instead of "face.stl"
4. Use "face-index-small.stl" instead of "face-index.stl"
5. Other models for face plate (face-dial.stl and face-letter.stl including other language versions) are common.
6. use "backplate-small.stl" instead of "backplate.stl".

Minimum version (for 200 x 200mm printer) is also available. It has no wall around the backplate. use files with "-200mm" suffix.