Introduction: Perpetual Calendar (200 Years)
The inspiration behind this calendar came from another Instructables member going by the name of "dahlkdg". Thank you sir!
I wanted to retain the feature of correct and conventional display of the calendar month (starts on Sunday, correct number of days), but wanted to make one that was smaller and eliminated the "handles" arrangement. Having four "disks" move independently from one another within an outer shell meant that it was tricky to move one disk without disturbing one or more of the others. So, I opened out the design and changed the setting method to one of aligning arrows.
The calendar has a 200 year range that includes the entire 20th century. I decided to include the past as I would guess that there might be more demand to use the calendar to find out what day of the week significant dates in history were rather than look so far ahead into the future so as to be outside the lifetime of those currently living.
The year disk can be made to use a narrower year range so that it looks less cluttered. If there is demand, I could upload a blank one for people to put their own year range in using an appropriate editor.
The originals were created using Microsoft Publisher and if required, the language dependent disks (month and front mask) editable files could be made available.
The simplicity of the design lends itself to being easily made with real materials and being no larger than the size of a CD, CD packaging (cases or sleeves) can be utilised for storing the calendar.
This project makes a prototype made of paper. By selecting different materials (wood, brass, plastic etc), the instructable could yield a useful tool or gift idea.
Step 1: Download and Print the PDF Files
Download the four PDF files and print them out (A4 size) onto card, stiff paper, self-adhesive label paper or whatever is required.
Step 2: Cut Out the Disks
Cut out the disks. They are all perfect circles and the month and day disks are identical in size to a CD (diameter 120mm). The small circles in the centre of each disk is identical in size to a CD's central hole (15mm diameter).
Using a sharp knife (and some care!) cut out the 14 small view holes in the year disk and the calendar display window in the front mask disk.
Step 3: Punch Holes
Using a pin, tack or needle, punch holes in the centre of each of the disks. The centre point of each disk is marked by crossed lines within the small central circle. Be as accurate as possible.
Step 4: Assemble the Disks
Starting with a pin, drawing pin or tack, thread the year disk through its centre hole and the printed side facing the head of the pin. Next, thread the month disc on top of the year disk with the printed side facing the blank side of the year disk. Thread the day disk on top of the month disk with the printed side facing the sharp end of the pin.
The month and day discs can also be stuck together to form one double sided disk. As these are also of the same dimensions as a CD (or DVD), the month and day disks can be glued to either side of a CD/DVD that no longer plays (for instance). This will provide a rigid back bone for the calendar as a whole.
Thread the front mask disk on top so that the printed side faces the sharp end of the pin. Lastly, place a cork over the sharp end of the pin and press it flat to the (printed) surface of the front mask.
Step 5: Setting the Calendar
- Find the required year and match its arrow with the arrow corresponding to the required month.
- Note the letter in the little window underneath the year in the same sector.
- Flip the calendar over and align the inner disk's arrow with the noted letter.
- The correct monthly calendar should now be shown in the window.
The letter associated with the year/month combination represents the day of the week the month starts.
- 31 day months - A=Sunday, B=Monday, ... G=Saturday
- 30 day months - H=Sunday, I=Monday, ... N=Saturday
- February (non leap year) - O=Sunday, P=Monday, ... U=Saturday
- February (leap year) - a=Sunday, b=Monday, ... g=Saturday
Within the central circle of the year disk lies a circle of days of the week (red for leap years). These indicate for their corresponding year sector the day of the week of the 1st of January of that year. The non leap year sectors simply follow one another as the eye goes round the disc in a clockwise fashion. This reflects the common scenario in that for any non leap year, the day of the week the following year starts is advanced by one day. Leap year sectors follow a different pattern where adjacent sectors are four years apart and the starting day of the week are two days apart.