Hello Shrem,

A calendar is a specific measure of time. The smallest unit of the calendar is a day. A day is an average time in which the earth completes one round on its axis. The time in which the earth travels around the sun is known a solar year.

Important Points:

• A year divisible by 4 is a leap year
• In the case of the century, leap year is that which is divisible by 400
• There are 365 days in an ordinary year, so there is 52 weeks+1 day. Hence, an ordinary year contain 1 odd day.
• There are 366 days in a leap year. Hence a leap year contain 2 odd days.
• There are 28 days in February in an ordinary year while in a leap year there are 29 days in February.
• There are 28 days in February in an ordinary year while in a leap year there are 29 days in February.
• The day of the week on 1st Jan 1 AD is Monday
• After 11 years the calendar is repeated
• The minute hand is also called the long hand while the hour hand is known as shorthand.
• In every hour, the minute hand gains 55 minutes on the hour hand
• The hands are in the same straight-line when they are opposite to each other or coincident
• In every hour hand coincide once
• The hands coincide 11 times in every 12 hours
• The minute hand moves 3600 in 1 hour while hour moves 300  in 1 hour

Hope it helps!