>>> datetime(2011, 9, 30) - datetime(1984, 5, 14) datetime.timedelta(10000)
irb(main):017:0> (Time.utc(2011, 9, 30) - Time.utc(1984, 5, 14)) / 60 / 60 / 24 => 10000.0
echo date_diff(date_create('1984-05-14'), date_create('2011-09-30'))->format('%a days'); => 10000 days