Mutate(yearweek = as. In column "yearweek" the years are sometimes wrong, in "yearweek2" they are corrected (rows 2 and 5). This codes provides some examples and a solution. For instance, (yyyy-mm-dd) is week 53 of year 2015, not 2016. If you want to get the week number with the year, Grant Shannon's solution using strftime works, but you need to make some corrections for the dates around january 1st. I provided a link to my simple geneorama package, but please don't rely on it too much because it's likely to change and not very documented. The best way to do this would be to add an offset to the offset. Of course, you can easily change the offset to make Monday first or whatever. Offset <- data.table(weekday = c('Sunday', 'Monday', 'Tuesday', 'Wednesday', I day weekday day_rounded weekday_rounded weeknumber # This seems to make internal sense with the "week" calculation # Now let's add the weekdays for the "rounded" dateĭt I don't understand the internal mechanics, but you can see what I mean with this example: library(data.table) Without these helpers, many of us would be lost.I think the problem is that the week calculation somehow uses the first day of the year. 2015 starts on Thursday, January 1st 2015 and ends on Thursday, December 31st 2015. This way we don’t forget important dates such as holidays, annual leave or exam weeks. The year 2015s maximum week number is WN 53. Almost everyone uses one, whether as a notebook or app on their mobile phone. The calendar has become a necessity to us all. Unfortunately the right week number can be off by up to 2 weeks. The rule of thumb to calculate the week number is based on the number of months from January to the last month multiplied by 4 plus the number of weeks in the current month. Hence business persons are best-informed when it comes to details about the current week number. Professionals working in the business sector set up their business appointments based on the calendar weeks. The calendar weeks serve different purposes. This day and god were extremely important to the ancient Romans. Sunday Sunday is named after the sun god Sol (lat. The Romans named the day after the Roman god of seed Saturn (lat. Saturday Saturday is derived from the Jewish Sabbath. dies veneris) and the Germanic goddess of love and marriage Freya. dies iovis).įriday Friday is derived from the Roman goddess of beauty Venus (lat. Thursday Thursday is named after the Germanic god of thunder Thor and the Roman god Jupiter (lat. dies mercoledi) and the Germanic god Wotan. Its name is derived from the Roman god Mercuris (lat. Wednesday Wednesday is also referred to as midweek. dies Martis) and the Germanic god of war Tyr. Tuesday Tuesday comes from the name of the Roman god of war Mars (Lat. Monday Monday is named after the Roman goddess Luna (lat. The Germanic peoples later translated each Roman god from Latin into Germanic. The Romans considered the sun and the moon planets as well. The Romans named the days after their gods, the seven ancient planets (Sun, Moon, Mars, Mercury, Jupiter, Venus and Saturn). In addition, years that are divisible by 100 but not by 400 are not leap years, as is the case with 1700, 1800, and 1900. To compensate for this inaccuracy, an extra day - February 29 - was introduced every four years. Christmas would end up being sometime in the summer. The earth rotates 365 days and 6 hours around the sun, which is longer than the standard calendar year. Why does a leap year have one day more than a normal year? When a normal year starts on a Thursday and also ends on one, it is 53 weeks long.Ī leap year also consists of 53 calendar weeks, beginning either on a Wednesday and ending on a Thursday or starting on a Thursday and ending on a Friday. The fourth of January is always in the first WN.Ī standard year has 52 weeks if it is not a leap year.The first calendar week starts with the first four days of the new year.There are no incomplete calendar weeks every week has exactly seven days.A new calendar week (week number) always begins on Monday.In countries such as the USA, Mexico, Australia and Canada the weeks start with Sunday as the first day of the week and end on Saturday. Since 1976 every week has started on a Monday and ended on a Sunday. The German-language calendar is not an exception. The international standard ISO 8601 is used to display the date and time. The calendar sets periods of time by combining days into weeks, weeks into months and months into years.
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