Spanish locale: del→de before year

The proper preposition before the year is «de». «del» is used informally for years after 2000, but «de» is still the preferred form. «del» doesn't really work for years before 2000.

Source: [Spanish Royal Academy's *Panhispanic Dictionary of Doubts*](http://lema.rae.es/dpd/srv/search?id=7Yloy2M3SD6pcC3Zyx).