Duration

The length of time from the start until the end of an event

Day

24 hours, from midnight to the midnight of the following day

a.m.

An abbreviation for ante meridiem (antemeridian) meaning ‟before midday” or morning

p.m.

An abbreviation for post meridiem (postmeridian) meaning ‟after midday” or afternoon that referring the time from midday to before midnight

Calendar

A systematic schedule of the year that is divided into days, weeks and months

Leap year

The year that has 366 days including February that has 29 days and it occurs every four years

Months (31 days)

January, March, May, July, August, October and December

Months (30 days)

April, June, September and November

February (regular year)

28 days

February (leap year)

29 days