# What is ISO Year week?

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## What is ISO Year week?

An ISO week-numbering year (also called ISO year informally) has 52 or 53 full weeks. That is 364 or 371 days instead of the usual 365 or 366 days. The extra week is sometimes referred to as a leap week, although ISO 8601 does not use this term. Weeks start with Monday and end on Sunday.

## How many weeks were there in 2009?

There are 53 weeks in 2009.

How is ISO week number calculated?

1. Step 1 – Calculate what the Monday of the Week for the Current Date is.
2. Step 2 – Calculate what the Thursday of the Week for the Current Date is.
3. Step 3 – Convert the Date Serial to the “Day of the Year”
4. Step 4 – Prepare for More Integer Math.
5. Step 5 – Divide the “Up-Rounded” Number of Days by 7 to Get the ISO Week Number.

### What is the current work week number?

Week 39
Week 39 is from Monday, September 27, 2021 until (and including) Sunday, October 3, 2021. The highest week number in a year is either 52 or 53. 2021 has 52 weeks.

### How many weeks were in 2008?

The year 2008 has 52 calendar weeks. 2008 begins on 01/01/2008 and ends on 31/12/2008. The first calendar week in 2008 begins on Monday, the 31/12/2007 and ends on Sunday, the 06/01/2008. The last calendar week in 2008 begins on Monday, the 29.12.

What number is 2009?

2,009 (two thousand nine) is an odd four-digits composite number following 2008 and preceding 2010. In scientific notation, it is written as 2.009 × 103. The sum of its digits is 11.

#### Is the ISO week date system a leap week?

The ISO week date system is a leap week calendar system that is part of the ISO 8601 date and time standard.

#### When does the ISO year start and end?

As per ISO standard 8601 and ISO standard 2015, Thursday is the middle day of a week. Hence, the ISO years always start on a Monday. For the above reasons, ISO year can start as yearly as 29th January or as late as 4th January of a Gregorian calendar. ISO years can have either 52 full weeks or 53 full weeks.

How is the ISO week date different from the Gregorian calendar?

Differences to other calendars. Solar astronomic phenomena, such as equinoxes and solstices, vary in the Gregorian calendar over a range spanning three days, over the course of each 400-year cycle, while the ISO Week Date calendar has a range spanning 9 days.

## When is the first day of the ISO year 2020?

The ISO year is slightly offset to the Gregorian year; for example, Monday 30 December 2019 in the Gregorian calendar is the first day of week 1 of 2020 in the ISO calendar, and is written as 2020-W01-1 or 2020W011.