A function checking the date is valid

dateCheckUpdated.rb

=begin rdoc
Checks that the supplied date has the correct date format '#YYYY:MM:DD' with the separators both be either - or : or /.
A year cannot start from the zero, while a month and a day can.
Performs additional checkings that the date is valid.
=end
def checkDateUpdated(aDate)
  matched =
    %r{
        (?<year>
        (^            #no input before the start
          [1-9]\d{3}  #a year cannot start from the zero
        )
      )
      (?<sep>-|:|/)   #a separator can be either - or : or /
      (?<month>
        (0[1-9])      #a month can start from the zero
        |
        (1[0-2])      #or it could be just 10, 11 or 12 of course
      )
      \k<sep>         #the 2nd separator must be the same as the 1st met
      (?<day>
        (0[1-9])      #a day can start from the zero
        |(1[0-9])     #or should fall into the range [1..31]
        |(2[0-9])
        |30
        |31
      )$              #marks there should be the end of the input
    }x.match(aDate)

    if (matched)
      day, month, year = matched[:day], matched[:month], matched[:year]
      day = day[-1] if day[0] == "0"
      month = month[-1] if month[0] == "0"

      year, month, day = year.to_i, month.to_i, day.to_i

      require 'date'
      begin
        date = Date.new(year, month, day)
      rescue ArgumentError => e
        return false
      end

      true
    else
      false
    end
end
 
date  = "2011:11:30"
print "date is #{checkDateUpdated(date) ? "" : "not "}correct"