There is no single, well-defined answer to this type of question, because it depends on how exactly you define a week, i.e., how you define what is the first week and the last week of the year.
EDIT: Since there are 365 days in 2013, there are 52 weeks and one day in every year - except leap years (when there's an extra day)
how many weeks left in 2013
28 weeks.
41 weeks.
52, and one day.
21.6 weeks
ten weeks
53 weeks
There are 26 weeks from July 1, 2013, to December 31, 2013.
From the first Sunday to the last Saturday of 2013 is 51 weeks.
how many weeks from 2nd Nov 2013 to 2nd march 2104
28 weeks and 5 days
4