Rails quirk: Adding to DateTime

Just came across a weird one with DateTime. Adding an int value will increment by a day, not a second as you may expect:

  1. $ x=1
  2. 1
  3. $ x.class
  4. Fixnum
  5. $ DateTime.new(2000, 1, 1, 0, 0, 0)+x
  6. Sun, 02 Jan 2000 00:00:00 +0000

But adding by a second is possible using explicitly 1.second. The strange thing is both inherit from FixNum and essentially act as the same number. So if you want it to mean seconds, one way to achieve it is use “x.seconds”.

  1. $ x=1.second
  2. 1 second
  3. $ x.class
  4. Fixnum
  5. $ DateTime.new(2000, 1, 1, 0, 0, 0)+x
  6. Sat, 01 Jan 2000 00:00:01 +0000

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