Provides accurate date and time measurements using Date#advance and Time#advance, respectively. It mainly supports the methods on Numeric. Example:

1.month.ago       # equivalent to Time.now.advance(:months => -1)
Methods
#
A
F
S
U
Attributes
[RW] parts
[RW] value
Instance Public methods
+(other)

Adds another Duration or a Numeric to this Duration. Numeric values are treated as seconds.

Source: show | on GitHub 

# File activesupport/lib/active_support/duration.rb, line 21
def +(other)
  if Duration === other
    Duration.new(value + other.value, @parts + other.parts)
  else
    Duration.new(value + other, @parts + [[:seconds, other]])
  end
end
-(other)

Subtracts another Duration or a Numeric from this Duration. Numeric values are treated as seconds.

Source: show | on GitHub 

# File activesupport/lib/active_support/duration.rb, line 31
def -(other)
  self + (-other)
end
==(other)

Returns true if other is also a Duration instance with the same value, or if other == value.

Source: show | on GitHub 

# File activesupport/lib/active_support/duration.rb, line 46
def ==(other)
  if Duration === other
    other.value == value
  else
    other == value
  end
end
ago(time = ::Time.current)

Calculates a new Time or Date that is as far in the past as this Duration represents.

Also aliased as: until

Source: show | on GitHub 

# File activesupport/lib/active_support/duration.rb, line 69
def ago(time = ::Time.current)
  sum(-1, time)
end
from_now(time = ::Time.current)
since(time = ::Time.current)

Calculates a new Time or Date that is as far in the future as this Duration represents.

Also aliased as: from_now

Source: show | on GitHub 

# File activesupport/lib/active_support/duration.rb, line 62
def since(time = ::Time.current)
  sum(1, time)
end
until(time = ::Time.current)