ruby - why does subtraction between dates return a Rational type? -

i trying perform subtraction operation on dates.

date_sent = date.parse("2013-01-01") #=> tue, 01 jan 2013 date_now = date.today  #=> wed, 04 sep 2013 days = (date_now - date_sent) #=> (246/1)

why date_now - date_sent return rational type?

it's expected behavior. docs:

d - other → date or rational

date.new(2001,2,3) - 1               #=> #<date: 2001-02-02 ...> date.new(2001,2,3) - date.new(2001)  #=> (33/1)

a rational type used because can express difference exactly:

diff = datetime.new(2001,2,3) - datetime.new(2001,2,2,1) #=> (23/24)

whereas float can't:

diff.to_f #=> 0.9583333333333334

Brazell