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# The Calendar

A calendar is generally used to measure time in a year or more, such as years, decades, millennium, and so on.

The calendar we all follow was originally devised by the Romans who chose the year of birth of Jesus Christ as their zero point. The time period before the birth of Christ is called BC (before Christ). So 800 BC represents 800 years before the birth of Christ.

The time period after the birth of Christ is called AD (Anno Domini, meaning year of our Lord).

The time difference between 500 BC and 200 AD is 500 + 200 =  700 years.

In modern times, a calendar typically displays a year, which can be also expressed as :

 1 year = 52 weeks = 26 fortnights = 12 months = 365 days = 366 days (during a leap year, which occurs every 4 years)

Some of the higher measurements of time are:

 1 decade = 10 years 1 century = 100 years 1 millenium = 1000 years 12 months = 1 year 3 months = year (quarter of a year) 6 months = year (half a year) 2 weeks = 1 fortnight

As we saw, a year has 12 months, and these 12 months (along with the number of days in each month are shown below):

 January = 31 days February = 28 days* March = 31 days April = 30 days May = 31 days June = 30 days July = 31 days August = 31 days September = 30 days October = 31 days November = 30 days December = 31 days

* Note : February will have 29 days when it is a leap year, that is why the leap year has one extra day (= 366 days).