Ruby, если даты находятся в диапазоне
d1 = DateTime.parse('2018/04/01')
d2 = DateTime.parse('2018/04/29')
outside = DateTime.parse('2018/04/30')
inside = DateTime.parse('2018/04/15')
# include?
(d1...d2).include?(d1) # true
(d1...d2).include?(d2) # false
(d1...d2).include?(outside) # false
(d1...d2).include?(inside) # true
(d1..d2).include?(d1) # true
(d1..d2).include?(d2) # true
(d1..d2).include?(outside) # false
(d1..d2).include?(inside) # true
# ===
(d1...d2) === d1 # true
(d1...d2) === d2 # false
(d1...d2) === outside # false
(d1...d2) === inside # true
(d1..d2) === d1 # true
(d1..d2) === d2 # true
(d1..d2) === outside # false
(d1..d2) === inside # true
# cover?
(d1...d2).cover?(d1) # true
(d1...d2).cover?(d2) # false
(d1...d2).cover?(outside) # false
(d1...d2).cover?(inside) # true
(d1..d2).cover?(d1) # true
(d1..d2).cover?(d2) # true
(d1..d2).cover?(outside) # false
(d1..d2).cover?(inside) # true
# between?
d1.between?(d1, d2) # true
d2.between?(d1, d2) # true
outside.between?(d1, d2) # false
inside.between?(d1, d2) # true
Healthy Hummingbird