class Time

def advance(options)

:minutes, :seconds.
:months, :weeks, :days, :hours,
The +options+ parameter takes a hash with any of these keys: :years,
Uses Date to provide precise Time calculations for years, months, and days. 
def advance(options)
  unless options[:weeks].nil?
    options[:weeks], partial_weeks = options[:weeks].divmod(1)
    options[:days] = (options[:days] || 0) + 7 * partial_weeks
  end
  unless options[:days].nil?
    options[:days], partial_days = options[:days].divmod(1)
    options[:hours] = (options[:hours] || 0) + 24 * partial_days
  end
  d = to_date.advance(options)
  time_advanced_by_date = change(:year => d.year, :month => d.month, :day => d.day)
  seconds_to_advance = (options[:seconds] || 0) + (options[:minutes] || 0) * 60 + (options[:hours] || 0) * 3600
  seconds_to_advance == 0 ? time_advanced_by_date : time_advanced_by_date.since(seconds_to_advance)
end