Julian and Gregorian calendars

Since my last post I have chosen to put the handling of logins on pause in order to be able to produce some visible progress. I have spend time on implementing some initial calendars which I’ll discuss in this post.

Postponing login solution

As mentioned in a previous post I’m interested in trying to monetize on the calendar application. Maybe by some subscription plans as currently indicated on the web site. For this I need to keep track of users and logins. However, as it will take me more time than assumed and I will not have anything to show until it is nearly finished, I’ve decided to put in on pause for a while. I will focus on producing a useful service first. Later I will revisit and determine how I might monetize; by subscription plans, donations or something else.

Julian and Gregorian calendars

According to Wikipedia, the Julian calendar was proposed by Julius Caesar in 46 BC as a reform of the Roman calendar. It became the predominant calendar in the Roman world, most of Europe, and in European settlements in the Americas and elsewhere. The average year in the Julian calendar is, however, longer than a solar year and the Gregorian calendar was developed as a correction. The Gregorian calendar is named after Pope Gregory XIII, who introduced it in October 1582 with the motivation of bringing Easter back to the time of the year in which it was celebrated by the early Church. To reduce the average year, the Gregorian calendar skips three leap years in 400 years compared to the Julian calendar (the years that are dividable with 100, but not 400). To deal with the drift between reality and the Julian calendar, 10 days were skipped at the introduction of the Gregorian calendar in October 1582, letting the 4th be followed by the 15th.

In Denmark we adopted the Gregorian calendar in 1700 at which point the drift had become 11 days. We skipped those in February jumping straight from the 18th of February to the 1st of March. Other countries switched to the Gregorian calendar at other times and in some countries like Sweden the switch took several years. Some Eastern Orthodox countries switched to the Gregorian calendar, but still calculate Easter from the Julian calendar. Greece was the last European country to adopt the calendar in 1923 and now most countries in the world are using the calendar for civil purposes according to Wikipedia.

Calendar application

As a start, I have implemented the Julian and Gregorian calendars in the calendar application. For both calendars, I determine the days and weekdays of the year and the falling of a few named days. I especially calculate the falling of Easter and use that to determine a few other named days in the year.

The application is still an early preview. It is only in English and the named days shows up as some cryptic texts that will need some translation at some point. There is also some functionality indicated in the application which is not implemented at the moment, but just indicates what’s to come.

Until next time

The next thing I will try to implement is a Danish calendar which is just the Julian calendar until 1699 and the Gregorian calendar from 1701 and then a mixture of the two in the year 1700. Afterwards I might try to look into translations, introducing calendars from more countries and/or some of the other functionality, e.g. to determine a date from a death date and an age.