Difference between ISO Calendar and Gregorian Calendar

Summary

The provided content outlines the differences between the ISO 8601 Calendar and the Gregorian Calendar, with a focus on how week numbering is handled differently in each system and how Tableau allows users to select their preferred calendar type for data analysis.

Abstract

The article discusses the distinct approaches to week numbering in the ISO 8601 and Gregorian calendars. The ISO 8601 calendar, reintroduced by ISO in June 1988, ensures that every week contains seven days, even if it means a year may have 53 weeks. The determination of the week number is based on the position of Thursday within the week that straddles two years. In contrast, the Gregorian calendar's week numbering begins on the first day of the year, which can result in the first and last weeks of the year being incomplete. The article also explains how Tableau enables users to choose between calendar types, which influences how weeks, days, and week numbers are calculated within the software for data analysis purposes.

Opinions

The ISO 8601 Calendar is presented as a solution to the problem of ensuring each year has a consistent number of weeks.
The article implies that the ISO 8601 Calendar is more logical for year-over-year comparisons because it standardizes the length of weeks in a year.
The Gregorian Calendar's approach to week numbering is seen as less consistent because the first and last weeks of the year can vary in length.
The functionality in Tableau to select a preferred calendar type is highlighted as a valuable feature for data analysis, suggesting that it simplifies calculations and ensures consistency in reporting.

Difference between ISO Calendar and Gregorian Calendar

ISO 8601 Calendar

The week numbering was reintroduced by ISO in June 1988 to solve the problem that each week in a year should have seven days even for the first and last week of the year.

Let’s suppose that a week is overlapping between two years then Thursday of this week decides whether it is an ISO week 53 of the previous year or the ISO week 1 of the next year.

If Thursday of the over-lapping week falls on or before 31st Dec then that whole week will be considered as ISO week 52/53 of the previous year or if Thursday falls on or after 1st Jan then it will be considered as ISO week1 of the next year.

Gregorian Calendar

In Gregorian Calendar Week numbering always starts from the 1st day of the year and the first and last week of the year doesn’t need to have 7 days. Let’s suppose that 1st Jan of a year is Saturday then, in that case, the first week will have only 2 days and same with the previous year that it will have only 5 days in the last week.

How to select your preferred Calendar type in Tableau?

Tableau provides you the functionality for selecting your preferred type of calendar for a data source. Which automatically allows tableau to calculate weeks, days, and week numbers for all the dates available in the data source based on the selection of calendar type.

Right-click on the data source in tableau and select date properties then after that from the pop up you can select your preferred calendar for the analysis.