Though most years have only 52 weeks (Except for leap years), Web TimeSheet reports may show days extended to Week 53.
This is because some days may fall outside the 52 weeks.
365 days / 7 days = 52.14 weeks.
Hence all the days of a year does not fall inside the 52 weeks.
Example: 1st and 2nd January 2010 falls under the last week of 2009.
When considering the year 2010, There are only 52 weeks, but these 2 days fall outside that, hence Web TimeSheet considers these 2 days as part of Week 1, therefore making the year have 53 weeks in Web TimeSheet reports, however in actual calendars the Year 2010 has 52 weeks only.