Weeknumber.in is created by me, Christian Schmidt, as a side project. I got the idea for the site when I was working for TV 2, a Danish national television station. Planning of TV ad campaigns was done based on weeks, and I was completely lost without a paper calendar showing week numbers. So I created this site as a tool for myself as well as others.
The site was originally launched in Danish in 2003 on Ugenr.dk. In 2010 I created this English-language version of the site, and since then it has been translated into several other languages, mostly using Google Translate. See the list of sites below.
Any feedback on the site would be very much appreciated. Please send your comments, suggestions and questions to.
About week numbers
Week numbers are commonly used in some European and Asian countries when referring to an entire week, e.g when planning projects, vacations etc. However, most people have troubles translating a week number into a date and vice versa, and a lot of software has poor support for week numbers. Thus the idea for this site arose.
This site uses week numbers as defined in the ISO 8601 standard (other systems exist, but they are not supported by this site): The first day of the week is Monday, and week 1 of a given year is the seven-day week containing 4 January. Week numbers are in the range 1 through 53, though most years only have 52 weeks (52 × 7 = 364 days, so the occasional week 53 covers the 365th day and the 366th day in leap years). Week 1 of a given year may start during the last days of the previous year (e.g. week 1, 2013 starts on Monday, 31 December, 2012), and likewise the last week of a given year (week 52 or 53) may end during the first days of the following year (e.g. week 52, 2011 ends on Sunday, 1 January, 2012).
Weeknumber.net in other languages
Weeknumber.in on social media
Follow Weeknumber.in on Facebook, Twitter or Mastodon and get updates with the current week number every Monday morning.