In a regular year, the average month is 365/12 = 30.42 days, while in a leap year, it is 366/12 = 30.50 days. The Gregorian (western) solar calendar has an average of 365.2425/12 = 30.44 days, fluctuating between 28 and 31 days. So there are actually fewer days in a year than in a month, but more come around to make up for it.

There are four seasons and two holidays: spring equinox and fall equinox, as well as the summer and winter solstices. These occur at **different times** of the year but on the same day. At other times of the year there are either three or five. There are several reasons why this is so: first, the Earth does not spin completely around itself but instead spins around its axis; second, the axis around which it spins is not fixed but rather moves back and forth like a spinning top's needle. Because of these two factors, each day is never exactly the same as the one before or after it; third, even when it is the same day, not all parts of **the world experience** all four seasons simultaneously.

A month consists of four full weeks plus a few days that range from zero (February in **most years**) to **three "extra" days** (January, March, May, July, August, October, and December). In leap years, February has 29 days, whereas April, June, September, and November each have **30 days**. In non-leap years, it averages 4-1/3 weeks every month. Months are based on the lunar cycle, so they can sometimes be slightly irregular (i.e., contain a few days more or fewer than the average). The only time when every month has exactly four weeks is in a year with an even number of days, such as 2016, because then the first week of January is always New Year's Day.

One month contains between 21 and 23 days. The longest month is Janaury; it contains 31 days. The shortest month is February; it contains 28 days. This is because our calendar is based on the solar cycle, not the lunar cycle. So each month contains either 29 or 30 sunrises and sunsets. The reason for this variation is so we can have some months with an odd number of days and others with an even number. For example, March has 26 sunrises and sunsets because two weeks plus a day equals March 4th, and March 15th is a Saturday, so the next day is Sunday, which makes the total number of sunrise days equal to 26.

It is important to note that although a month contains between 21 and 23 days, this does not mean that each day is used up equally fast.

Except for years that are divisible by 100 but not by 400, a leap year occurs every four years. Calendar of the months of the year

# | Month Name | Days in Month |
---|---|---|

4 | April | 30 days |

5 | May | 31 days |

6 | June | 30 days |

7 | July | 31 days |

Leap Day occurs every four years on average. It is the date we add February 29 to our calendar. As a result, the year becomes 366 days long rather than the standard 365. Leap years are years that include **a leap day**. If we exclude February 29, then there are 364 other possible days that could be called "leap days". Years divisible by four but not by 100 are usually not leap years, except if they are also divisible by 400 (such as 2016) or 500 (such as 2036). However, it can sometimes happen that a year with a common divisor of 4 goes over or under these limits and becomes a leap year. For example, 1998 was a leap year but not 2000. The rule for determining whether a year is a leap year is based on the number of times 4 divides into the year without remainder or not at all (that is, without losing any digits). For example, 4 times 0 equals 0 because 0 is even. 4 times 1 equals 4 because 4 does not divide into 1 without leaving **1 digit** in both cases. Therefore, 1998 was a leap year.

Leap years were originally established so farmers could work the land during certain periods when it would be easier on their animals to provide food when nutrients are most needed. Humans need sleep too! Before the introduction of agriculture, people lived in small tribes of about 150 people or less.

A calendar year is made up of 365 days (52 weeks + 1 day). Every average year has **one unusual day**. A leap year has **two odd days**. (76 times 1 + 24 times 2) odd days Equals 124 odd days.

An odd day in a year can be either a weekday or a weekend day. If it's a weekday, that means that there are 123 regular days in the year. If it's a weekend, that means that there are 122 regular days in the year. The 1 unusual day is called an odd day because it does not belong to **any particular month**.

Odd days occur because when a year is divided by four, both the remainder and the result are always equal to 1. For example, if you divide 2000 by 4, then you would expect 500 to be the answer because this is what happens when you divide any number by 4. But instead, 1000 is the answer because February has only 30 days instead of 31. This causes an issue for calendars because people want to know how many days there are in a year. If we just add up all the numbers from 1 to 12, we get 365. But since some months have fewer than 30 days, this number needs to be adjusted. We can see that 2000 was an even year so it had 364 plus 1 extra day. Since 2004 is an odd year, it too will have 1 additional day.

A well-known rhyme helps people remember how many days are in each month: "September, April, June, and November have thirty days." Except for February, which has twenty-eight days clear and twenty-nine in each leap year, the others have thirty-one. The calendar year begins on New Year's Day, January 1. The first day of a month is called its "first day" or "calendar day"; other days may be "second", "third", etc., depending on their position in the month.

There are four seasons and they are called spring, summer, winter, and fall. These words are used to describe **the weather conditions** corresponding to the changing of the seasons. Spring starts around late February or early March and lasts until **late April** or early May. Summer from late April or early May through mid-August. Winter from mid-November through mid-January. Fall from mid-January through mid-February.

The number of days in each month is usually given before or after, or both before and after the date. So, the number of days in September is about 290. The word "month" comes from the Latin mensis, meaning "piece of hair worn by slaves," because it was once made up of pieces of leather attached to a slave's skin. Modern months are based on the lunar cycle, but before that they were based on **the solar cycle**.