The Calendar Week
Everybody knows it, everybody has heard about it, still, to many of us it remains rather unfamiliar: the calendar week. To make matters worse, the confusion starts anew every year: It is the first of January, hence the first calendarweek of the year. Well, that depends. On where you are. In some places the first calendar week of the year start with the first of January and it others it does not. Or rather in does not in four out of seven cases.
Confusing? You bet! But this is where come in to let you in on some of the facts about the calendar week. :-)
What is the Calendar Week?
In Europe the calendar week is a week that begins with Monday and ends with Sunday. Altogether, the year usually has 52 calendar weeks.
When does the first calendar week of the year actually begin?
In Europe, the first calendar week of the year is the week that contains four days of the new year.
If the 1st of January happens to be a Tuesday, the first calendar week of the year starts on Monday the 31st of December, because this week contains six days of the new year (Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday).
If, however, the 1st of January happens to be a Friday, the first calendar week of the years starts on Monday, the 04th of January, because the previous week only contains three days of the new year (Friday, Saturday, Sunday).
Is there an official definition for the calendar week?
Yes, there is. ISO 8601, which spcifies Monday as the first day of the week.
Does the definition for the calendar week apply internationally?
Yes and no. Many countries use this approach. However, quite a number of other countries, such as the USA, Canada, Mexico and Australia, start their week on Sunday. Furthermore, the first calendar week always starts on the 1st of January, no matter which day of the week this happens to be.
In the Middle East the week predominantly starts on Saturday. Like in North America and Australia, the first calendar week of the year starts with the 1st of January, regardless of the weekday.
Is There an Interntional Notation for Calendar Weeks?
Yes, there is. According to ISO 8601 the notation is as follows:
YYYY-Www or YYYYWww
YYYY-Www-D or YYYYWwwD
Hence, in Great Britain, Monday, the 31st of December 2013 would be noted as follows:
In the USA, however, it would be 2013-W01-2
And in the Middle East 2013-W01-3.