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 .