# File lib/ri_cal/core_extensions/time/calculations.rb, line 117
        def iso_weeks_in_year(wkst)
          iso_year, week_one_start = *iso_year_and_week_one_start(wkst)
          probe_date = week_one_start + (7*52)
          if probe_date.iso_year(wkst) == iso_year
            53
          else
            52
          end
        end