Simplify the following text for a Grade 8 native English-speaking person.
Original: Year 1661 ( MDCLXI ) was a common year starting on Saturday ( link will display the full calendar ) of the Gregorian calendar and a common year starting on Tuesday of the 10-day slower Julian calendar .
Simplified: 1661 was a common year starting on a Saturday in the Gregorian calendar , and a common year starting on a Tuesday in the Julian calendar .