[docs] Little mistake on datetime page

[Геннадий Пилипенко]

Hello!

http://docs.python.org/library/datetime.html#timedelta-objects

In examples:

---

>>> ten_years = 10 * year
>>> ten_years, ten_years.days // 365
(datetime.timedelta(3650), 10)

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should be:

---

>>> ten_years = 10 * year
>>> ten_years, ten_years.days // 3650
(datetime.timedelta(3650), 3650)

---

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Sincerely, Gennady