Original: Year 1668 (MDCLXVIII) was a leap year starting on Sunday (link will display the full calendar) of the Gregorian calendar (or a leap year starting on Wednesday of the 10-day slower Julian calendar).
Simplified: February 13 Lisbon - Peace Treaty between Afonso VI of Portugal and Carlos II of Spain, by mediation of Charles II of England where it is recognized the legitimity of the Portuguese monarch.