Hi and welcome to my website. Here you can find out how to add week numbers to Google Calendar. I have made a custom calendar which adds small week number icons to the title bar of the first day of every week. You can see an image of how it looks below. You can add these week numbers to your own calendar with the press of a button.

You can also add a gadget that displays week numbers to the right of your calendar.

Note: Google have recently made their own week numbers, so you might want to check that out. There are instructions on how to add their calendar a little further down on this page.

Add the week numbers

To add my week numbers, simply use this box:

Here is an image showing how it will look when you have added the calendar. The image to the right shows the gadget.

Pretty neat, right? I hope these week numbers will make your life easier. I have hosted this calendar since 2006 and it currently contains week numbers throughout 2015.

You can also add the gadget to Gmail by using Gmail Labs and adding this address: https://sites.google.com/site/gcalweeknumbers/Home/calendar-gadget.xml

You can remove the week numbers just as you would any other calendar. Simply go to your settings and press "Unsubscribe". If you just want to turn them off for a while, you can simply press the calendar called "Week Numbers" in your calendar list and the week numbers will disappear until you press it again.

Week numbers from Google

Google have finally gotten their act together and have added a pretty easy way to add official week numbers, if you know where to look. You have to go to a place called "Interesting Calendars." To get there, press the dropdown button () in the box called "Other calendars", then press "Browse Interesting Calendars," then go to the tab called "More" and subscribe to the calendar called "Week Numbers." In my test it appears that it adds the same calendar regardless of what language you use, and the week numbers are always displayed on Mondays. Google's week numbers look like this: .

I will continue to maintain my week numbers as long as people use them. And to be honest, I like my icons better. ;)

The rest of this page is about my week numbers.

Ensuring correctness

Due to the fact that some countries number weeks a little differently, I encourage you to verify that my week numbers are correct in your country. Pick up a local calendar and make sure the week numbers match. Note that traditional paper calendars often make mistakes with week 53, where they usually label it as week 1. But if you look at the calendar for the next year, the error should be fixed.

Mobile support

Your mileage may vary. Don't bug me about it.

Customizing the week numbers

Use this third party website to generate custom week numbers for your own use: http://optics.eee.nottingham.ac.uk/matt/weeknumbers/weeknumbers_form.php

I can not help you customize the week numbers. All the information you will need to create your own calendar like this is on the bottom of this page and in Google's official documentation.

About the author

Week numbers made by Stefan Sundin. The current icons were made by Marco Baumgarten.

I have also made another calendar which adds Swedish name-days (namnsdagar) to your calendar. If you are a swede, check it out here.


  • 2012-09-10
    I am aware of the issue where several duplicate events have been added to the calendar. There seems to be an issue where other people can invite my week number calendar to events, and these will appear to everyone subscribed to the calendar. I have reported the issue to google (here). If you want this issue to be resolved once and for all, please add a comment in the thread to let Google know this is a serious problem. For a quick fix, you can unsubscribe to this calendar and instead start using Google's official week numbers (instruction above). Please be patient and I am confident this issue will be resolved. Thank you.
    Posted Sep 10, 2012, 3:02 AM by Stefan Sundin
  • 2011-09-03
    Sometimes I wish I had a direct line to the GCal team.
    Posted Sep 3, 2011, 12:49 PM by Stefan Sundin
  • 2010-10-06
    Okay. I have received some feedback on the experiment I have been running (see post below this one).

    From what I could determine, there are two negative side effects from changing the length of the week number events. 1) All days are marked as busy (all days are bold in the mini-calendar). Previously only the first day in the week was marked as busy. 2) The week numbers appear on every day in the Agenda view.
    Despite of this, I have decided that the benefits outweigh the side effects, and I will apply this change to all week numbers in the coming days.

    For those of you who despise this change, there is a remedy! You can simply switch to Google's own week number calendar (instructions above). Their calendar is exactly the same as my calendar was before, with the exception of a different icon.

    My final thoughts on this is that I don't think Google has successfully added week numbers to Google Calendar. I think week numbers need to be integrated in the same manner as normal date numbers. Any "solution" that requires an extra calendar will be flawed in some way. My hopes that Google will make week numbers a first class citizen is unfortunately very low.
    Posted Jun 12, 2011, 11:29 AM by Stefan Sundin
  • 2010-09-05
    I am currently running an experiment that should make it more convenient to view the week numbers on mobile phones like Android. I have modified to length of the events so that they span the whole week. This should make the icon appear on every day when using the day view. The calendar will look exactly the same on the web, so you should not notice any difference there. The only difference I have noticed is that the week number icon appears on every day when you are using the day view there too, but that is expected and also pretty nice.

    I have only applied this for week 37, 38 and 39 and only on the Mondays calendar. If this experiment works out then I will proceed with updating all future week numbers.

    I got this tips from a user like yourself and that is how this update started. Note that I do not own an Android device myself and therefore your feedback is important! Report any problem to me!
    Posted Sep 5, 2010, 3:11 AM by Stefan Sundin
Showing posts 1 - 4 of 11. View more »


Adding the week numbers manually

If the button on the top of the page didn't work, then you can try these links:

If you are still unable to add the week numbers, then you can try to add them from within Google Calendar. This also works in Google Apps. Just enter this text in the text field in the "Other calendar" box to the left in Google Calendar:

  • Mondays: g0k1sv1gsdief8q28kvek83ps4@group.calendar.google.com
  • Sundays: d8u7iiljjpfibev3cd8emgau78@group.calendar.google.com


If you couldn't add the gadget above, then try this link. If that didn't work either, then use the labs feature "Add gadget by URL" and add this address: http://sites.google.com/site/gcalweeknumbers/Home/calendar-gadget.xml
A nice thing to remember is that almost everywhere where you can add a gadget by URL, you should be able to add this gadget.

Google Apps users

Google Apps users can make a direct link to add the week numbers to their domain. Simply edit these links to your domain name:

  • Mondays: https://www.google.com/calendar/hosted/example.com/render?cid=g0k1sv1gsdief8q28kvek83ps4@group.calendar.google.com
  • Sundays: https://www.google.com/calendar/hosted/example.com/render?cid=d8u7iiljjpfibev3cd8emgau78@group.calendar.google.com

Just remember to replace example.com with your domain!

Error message

You might get the error message "The following are not Google Calendar users: g0k1sv1gsdief8q28kvek83ps4@group.calendar.google.com" when opening Google Calendar. It has only happened a few times, but each time it has resolved itself after a few days. I suspect this happens when Google's servers are having some troubles. There is nothing I can do about it, just sit tight and it will go away after a few days. You can also consider using Google's week numbers, described above.

One user sent me some instructions on how he or she worked around this error message:

  1. Go to settings in Google calendar.
  2. Go into the calender that gives you the message and check your calendar's time zone.
  3. Go back to Settings and when you are there click on the tab called General.
  4. Now you are going to look at "Your current time zone".
  5. If it's different, change the general timezone to the timezone of you problematic calendar.
  6. Save this setting.
  7. Check if the calender is working again.
  8. Change your general timezone back to the previous timezone.
I hope this will work. I have not tried it myself so your mileage may vary.

How I made it

Way back in 2006, when Google Calendar was created, there was no support for week numbers. Some people created ordinary day events to keep track of the weeks. Later that year, Google launched support for "Web Content Events", which are small icons that are displayed in the title bar of each day. After thinking about this for a while, I decided to create my own week numbers calendar with web content events. I checked the Google Calendar documentation for information on how I could add Web Content Events. The iCal solution looked pretty simple, so I decided to try that first. Each week has a 16×16 image associated with it which is displayed in the title bar.

I created a test iCal file with one entry, which worked. After a few tries I finally got a format I liked, and made a dirty php-script to generate events for an entire year. I then uploaded all the week number images to Google Sites, generated iCal files to supply weeks from January 2006 to December 2013 (now 2015), and uploaded them to a new shared calendar, which you can use with the click of a button. A lot of work by me, a very easy solution for you. ;)

And so, on October 23, 2006, I posted a thread in the Google Calendar help group, announcing this calendar. It was an instant hit and I have been supporting it ever since. Since then, the calendar has been through a move from Google Pages to Google Sites, several iterations and several icon changes. My only regret is that I do not know how many people are using the calendar, but I'm sure it's a lot. The site gets about 8000 unique visitors each month. You can see a pretty graph here (statistics from May 2009 to January 2013).

You can download all the files I have used when doing this calendar here, which includes the iCal files, the icon files and the php-script. If you want, you can grab the php-script individually.

Note: When you import events into your calendar there is usually a delay before the events appear. Wait at least one hour before doing anything foolish like importing the file again! I also recommend to import the events into a new calendar so you can easily remove everything.

If you are going to do something similar you should read up on weeks, it's not as simple as you might think, e.g., do you know when a year has 53 weeks instead of 52? Wikipedia has a pretty good explanation.