April 8, 2012 is exactly 17 weeks after December 11, 2011.
39 weeks
From the date of this question 26 April 2011, there are 10 weeks.
52 weeks rounded up.
105 weeks
As today is December 5, 2010 there are 145 days until April 29, 2011.
90 weeks and 1 day.
130 weeks and 2 days.
3 weeks&1 day. 22 days.
Pottermore was supposed to open in October 2011. Unfortunately, the opening was delayed until April 2012.
When the question was asked, on the 9th of February in 2011, the answer was 5 weeks and 3 days. On the day the question is being answered, the 31st of December 2016, it is 302 weeks since the 19th of March 2011.
8.6 weeks
Exactly 11 weeks after December 20, 2011 is March 6, 2012.