Historical clue formulations

• "Prospero Año ___!" — 2017-06-28
• ___ Mundo (what Cristóbal Colón explored) — 2015-09-29
• ___ Laredo, Mexico — 2010-07-06
• ___ León (Mexican state bordering Texas) — 2009-06-11
• New, to Neruda — 1999-07-06
• Opposite of viejo — 1996-12-25