Method: Time#change

Defined in:
lib/active_support/core_ext/time/calculations.rb

#change(options) ⇒ Object

Returns a new Time where one or more of the elements have been changed according to the options parameter. The time options (:hour, :min, :sec, :usec, :nsec) reset cascadingly, so if only the hour is passed, then minute, sec, usec, and nsec is set to 0. If the hour and minute is passed, then sec, usec, and nsec is set to 0. The options parameter takes a hash with any of these keys: :year, :month, :day, :hour, :min, :sec, :usec, :nsec, :offset. Pass either :usec or :nsec, not both.

Time.new(2012, 8, 29, 22, 35, 0).change(day: 1)              # => Time.new(2012, 8, 1, 22, 35, 0)
Time.new(2012, 8, 29, 22, 35, 0).change(year: 1981, day: 1)  # => Time.new(1981, 8, 1, 22, 35, 0)
Time.new(2012, 8, 29, 22, 35, 0).change(year: 1981, hour: 0) # => Time.new(1981, 8, 29, 0, 0, 0)

Raises:

  • (ArgumentError) 


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# File 'lib/active_support/core_ext/time/calculations.rb', line 123

def change(options)
  new_year   = options.fetch(:year, year)
  new_month  = options.fetch(:month, month)
  new_day    = options.fetch(:day, day)
  new_hour   = options.fetch(:hour, hour)
  new_min    = options.fetch(:min, options[:hour] ? 0 : min)
  new_sec    = options.fetch(:sec, (options[:hour] || options[:min]) ? 0 : sec)
  new_offset = options.fetch(:offset, nil)

  if new_nsec = options[:nsec]
    raise ArgumentError, "Can't change both :nsec and :usec at the same time: #{options.inspect}" if options[:usec]
    new_usec = Rational(new_nsec, 1000)
  else
    new_usec = options.fetch(:usec, (options[:hour] || options[:min] || options[:sec]) ? 0 : Rational(nsec, 1000))
  end

  raise ArgumentError, "argument out of range" if new_usec >= 1000000

  new_sec += Rational(new_usec, 1000000)

  if new_offset
    ::Time.new(new_year, new_month, new_day, new_hour, new_min, new_sec, new_offset)
  elsif utc?
    ::Time.utc(new_year, new_month, new_day, new_hour, new_min, new_sec)
  elsif zone.respond_to?(:utc_to_local)
    new_time = ::Time.new(new_year, new_month, new_day, new_hour, new_min, new_sec, zone)

    # Some versions of Ruby have a bug where Time.new with a zone object and
    # fractional seconds will end up with a broken utc_offset.
    # This is fixed in Ruby 3.3.1 and 3.2.4
    unless new_time.utc_offset.integer?
      new_time += 0
    end

    # When there are two occurrences of a nominal time due to DST ending,
    # `Time.new` chooses the first chronological occurrence (the one with a
    # larger UTC offset). However, for `change`, we want to choose the
    # occurrence that matches this time's UTC offset.
    #
    # If the new time's UTC offset is larger than this time's UTC offset, the
    # new time might be a first chronological occurrence. So we add the offset
    # difference to fast-forward the new time, and check if the result has the
    # desired UTC offset (i.e. is the second chronological occurrence).
    offset_difference = new_time.utc_offset - utc_offset
    if offset_difference > 0 && (new_time_2 = new_time + offset_difference).utc_offset == utc_offset
      new_time_2
    else
      new_time
    end
  elsif zone
    ::Time.local(new_sec, new_min, new_hour, new_day, new_month, new_year, nil, nil, isdst, nil)
  else
    ::Time.new(new_year, new_month, new_day, new_hour, new_min, new_sec, utc_offset)
  end
end