class Date

def advance(options)

any of these keys: :years, :months, :weeks, :days.
Provides precise Date calculations for years, months, and days. The +options+ parameter takes a hash with 
def advance(options)
  d = self
  d = d >> options[:years] * 12 if options[:years]
  d = d >> options[:months] if options[:months]
  d = d + options[:weeks] * 7 if options[:weeks]
  d = d + options[:days] if options[:days]
  d
end