class Time

def advance(options)

Time.new(2015, 8, 1, 14, 35, 0).advance(weeks: 1) # => 2015-08-08 14:35:00 -0700
Time.new(2015, 8, 1, 14, 35, 0).advance(days: 1) # => 2015-08-02 14:35:00 -0700
Time.new(2015, 8, 1, 14, 35, 0).advance(hours: 1) # => 2015-08-01 15:35:00 -0700
Time.new(2015, 8, 1, 14, 35, 0).advance(minutes: 1) # => 2015-08-01 14:36:00 -0700
Time.new(2015, 8, 1, 14, 35, 0).advance(seconds: 1) # => 2015-08-01 14:35:01 -0700

:seconds.
:weeks, :days, :hours, :minutes,
takes a hash with any of these keys: :years, :months,
according to the proleptic Gregorian calendar. The +options+ parameter
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.fetch(:days, 0) + 7 * partial_weeks
  end
  unless options[:days].nil?
    options[:days], partial_days = options[:days].divmod(1)
    options[:hours] = options.fetch(:hours, 0) + 24 * partial_days
  end
  d = to_date.advance(options)
  d = d.gregorian if d.julian?
  time_advanced_by_date = change(:year => d.year, :month => d.month, :day => d.day)
  seconds_to_advance = \
    options.fetch(:seconds, 0) +
    options.fetch(:minutes, 0) * 60 +
    options.fetch(:hours, 0) * 3600
  if seconds_to_advance.zero?
    time_advanced_by_date
  else
    time_advanced_by_date.since(seconds_to_advance)
  end
end