However, I've recently heard two alternate shortened forms, both from Mexicans (I am 100% sure I heard correctly):
mil nueve noventa y siete
mil nos noventa y siete
Has anyone else ever heard these? Are the same or other shortened forms used in other countries? Do parallel forms exist for earlier centuries, or only for the 1900s?
Are there other languages which would most "correctly" read out the whole year, but have shortened forms? How acceptable are they? (Casual speech only? Formal speech? Writing?)