Ruby Language DateTime Add/substract days to DateTime
Example
DateTime + Fixnum (days quantity)
DateTime.new(2015,12,30,23,0) + 1
# => #<DateTime: 2015-12-31T23:00:00+00:00 ((2457388j,82800s,0n),+0s,2299161j)>
DateTime + Float (days quantity)
DateTime.new(2015,12,30,23,0) + 2.5
# => #<DateTime: 2016-01-02T11:00:00+00:00 ((2457390j,39600s,0n),+0s,2299161j)>
DateTime + Rational (days quantity)
DateTime.new(2015,12,30,23,0) + Rational(1,2)
# => #<DateTime: 2015-12-31T11:00:00+00:00 ((2457388j,39600s,0n),+0s,2299161j)>
DateTime - Fixnum (days quantity)
DateTime.new(2015,12,30,23,0) - 1
# => #<DateTime: 2015-12-29T23:00:00+00:00 ((2457388j,82800s,0n),+0s,2299161j)>
DateTime - Float (days quantity)
DateTime.new(2015,12,30,23,0) - 2.5
# => #<DateTime: 2015-12-28T11:00:00+00:00 ((2457385j,39600s,0n),+0s,2299161j)>
DateTime - Rational (days quantity)
DateTime.new(2015,12,30,23,0) - Rational(1,2)
# => #<DateTime: 2015-12-30T11:00:00+00:00 ((2457387j,39600s,0n),+0s,2299161j)>
