Recycling old Calendars

When surfing an auction site I found a pocket calendar I possessed in my early youth: the Ensslin-Schüler-Taschenbuch 1974.

As a ten-year-old it fascinated me, because it not only contained the calendar of that year but also useful information like a complete survival guide (how to navigate without compass, to make fire, to source water, to build a tent,  to track foot steps, to use morse code, to leave signs, …), a table that allows to calculate the week day for any given date and a contest on how many different objects can be put into one matchbox.

When I considered buying it, I thought it would be useless because the calendar would not match this year’s calendar. But, what would a calendar need to match to another year? A given date (eg. Jan, 1st)  has to fall on the same week day and both years have to be either leap years or not.

I wrote a small program that compares different years for these conditions and found that I could reuse this calendar of 1974 again in 2019. However, many public holidays like (Easter, Whitsun, German Carnival, Ascension Day, Corpus Christi) are floating and match in some years only.

If you use your calendar as a diary, you can find a lot of “on this day”-reminders in your old calendar.

On my way to the attic now

In year … re-use old calendar of … YC
Re-use old calendar of … in year …CY