What Week Number is the Week Begining December 28, 2009?

One of the fun parts of my job is that on any given day I speak to people all over the world, and in the process I learn quite a bit about different ways people live, work, play or in this case even look at a calendar differently all over the world. Speak to most Americans (myself included) and you will find that week numbers are not a particularly big deal, but talk to many Europeans and you find that quite a bit of planning is done based on week numbers. So a few weeks ago I started receiving questions about the week number for the week beginning December 28, 2009, I took a look at my Notes calendar which told me it was Week 1 of 2010 however what I was being told by my colleagues was that it should be week 53 of 2009. A quick google search led me to my friend Mikkel who had picked this up and explained it  as follows

Got a call from a customer the other day who could not understand that the week numbers that showed up in his Notes 8.x calendar was different from the ones on this printed wall calendar. The reason for this is that by default Notes 8 uses the operating system default for calculating week numbers. Here in Denmark we use the ISO 8601 standard which is a little bit different. It is my understanding that previous releases of Notes automatically used the ISO standard. I could be wrong though. Thankfully the Notes developers know about these regional differences and there is an option to change the way week numbers are calculated. To change it open File/Preferences… and open the “Calendar and To Do/Regional Settings” page. On the bottom you’ll find a option to change between using the operating system default and using the ISO standard. There even is a way of doing custom week numbers if that’s needed.

lekkimworld: A word about week numbers Seems logical enough so I went in to my Notes Preferences / Calendar and To Do / Regional Settings, and changed the setting from “Use my operating system” to “Always use the ISO standard” sure enough I went back and checked my calendar and it was now week 53 So far so good, Notes lets you pick the style that works for you.   Now lets say you wanted to push this out via a policy, you can do so by pushing out a Notes INI Entry as follows FooterWeekNo=1 = Use my operating system regional settings FooterWeekNo=2 = ISO Standard FooterWeekNo=3 = Custom Week Numbers If you choose option number 3 you then also need to set FirstDayInYear=1 (where 1 is Sunday, 2 is Monday etc) MinDaysInFirstWeek=1 If you really want to understand the finer points of all this you can read the explanation of the ISO 8601 Standard (I strongly recommend a strong cup of coffee to go along with it!)