11 August 2021
In order to get the correct music on the correct date you obviously need to create a calendar of those dates... And that is a bit of a challenge.
Bach wrote both liturgical and wordly cantatas, so you need to get the correct dates for both kind of cantatas to create a correct calendar. The wordly cantatas all have a fixed date (like e.g. someone's birthday), but the liturgical days require a bit of calculation to get the correct calendar. The problem is that the dates in a liturgical year depend on three components:
In short, a liturgical year is structured as follows:
What makes the calculation of a liturgical year a bit strange is that Christmas has a fixed date (December 25) but a variable weekday, and Easter is the opposite: a variable date but a fixed weekday (Sunday). And their occurences in the year interfere with each other: if Christmas falls on a Monday makes a big difference, and an early or late Easter of course as well:
As you can imagine there are differences between liturgical calendars observed by the Catholic church or the Orthodox churches; I'm applying a pragmatic approach to create the Lutheran liturgical calendar which fits the Bach cantatas.
As an example, let's calculate the liturgical dates for 2025. These are the necessary steps:
So now we've calculated the variable dates for the year 2025, but in fact we have calculated the last part of the liturgical year 2024-2025, and the first part of the liturgical year 2025-2026... Which means you need to do these calculations for two subsequent calendar years in order to constitute one liturgical calendar. Cumbersome, but this works for me. Always interested to hear if there are easier (or more correct) ways to do it.
Next, add the fixed dates in the liturgical calendar:
And to complete my Bach cantatas calendar, I've added all occasions for which a cantata was created (or some I've added myself like Bach's birthday and death):
That makes up the complete Bach cantatas calendar as I see it. Would love to hear what you think of it, and especially if I have something wrong. Feel free to contact me at email@example.com.