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- 

        # Date.-

(from ruby core)
---
    d - other  ->  date or rational

---

Returns the difference between the two dates if the other is a date
object.  If the other is a numeric value, returns a date object pointing
`other` days before self.  If the other is a fractional number, assumes
its precision is at most nanosecond.

    Date.new(2001,2,3) - 1   #=> #<Date: 2001-02-02 ...>
    DateTime.new(2001,2,3) - Rational(1,2)
                             #=> #<DateTime: 2001-02-02T12:00:00+00:00 ...>
    Date.new(2001,2,3) - Date.new(2001)
                             #=> (33/1)
    DateTime.new(2001,2,3) - DateTime.new(2001,2,2,12)
                             #=> (1/2)

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