You might want to be able to view week numbers in Google Calendar, but Google hasn't released such a feature yet. Maybe you've used the ISO8601 calendar, or even made your own week numbers, but in my opinion using a day event to display the week number is kinda ugly.

Google has released a new feature since Google Calendar was created; Web Content Events. It gives Google Calendar the possibility to display events in the title bar of each day as small icons. I found out that you can only add these kind of entries by either uploading an iCal file or using the Google Calendar API, which only technically inclined people know how to do.

Reference : http://sites.google.com/site/gcalweeknumbers/googlecalendarweeknumbers