why does a year have 365 days?

Answer 1

The motion of the Earth in its orbit (and therefore the apparent motion of the Sun among the stars) is not completely regular. This is due to gravitational perturbations by the Moon and planets. Therefore the time between successive passages of a specific point on the ecliptic will vary. Moreover, the speed of the Earth in its orbit varies (because the orbit is elliptical rather than circular). Furthermore, the position of the equinox on the orbit changes due to precession. As a consequence (explained below) the length of a tropical year depends on the specific point that you select on the ecliptic (as measured from, and moving together with, the equinox) that the Sun should return to.
Therefore astronomers defined a mean tropical year, that is an average over all points on the ecliptic; it has a length of about 365.24219 SI days. Besides this, tropical years have been defined for specific points on the ecliptic: in particular the vernal equinox year, that start and ends when the Sun is at the vernal equinox. Its length is about 365.2424 days.
An additional complication: We can measure time either in "days of fixed length": SI days of 86,400 SI seconds, defined by atomic clocks or dynamical days defined by the motion of the Moon and planets; or in mean solar days, defined by the rotation of the Earth with respect to the Sun. The duration of the mean solar day, as measured by clocks, is steadily getting longer (or conversely, clock days are steadily getting shorter, as measured by a sundial). One must use the mean solar day because the length of each solar day varies regularly during the year, as the equation of time shows.
As explained at Error in Statement of Tropical Year, using the value of the "mean tropical year" to refer to the vernal equinox year defined above is, strictly speaking, an error. The words "tropical year" in astronomical jargon refer only to the mean tropical year, Newcomb-style, of 365.24219 SI days. The vernal equinox year of 365.2424 mean solar days is also important, because it is the basis of most solar calendars, but it is not the "tropical year" of modern astronomers.
The number of mean solar days in a vernal equinox year has been oscillating between 365.2424 and 365.2423 for several millennia and will likely remain near 365.2424 for a few more. This long-term stability is pure chance, because in our era the slowdown of the rotation, the acceleration of the mean orbital motion, and the effect at the vernal equinox of rotation and shape changes in the Earth's orbit, happen to almost cancel out.
In contrast, the mean tropical year, measured in SI days, is getting shorter. It was 365.2423 SI days at about AD 200, and is currently near 365.2422 SI days.

Answer 2

A year is 365 days because that is the amount of time it takes the world to revolve around the sun. It actually takes 365 and 1/4 which is why we have a leap year every 4 years.

Answer 3

1) The 365 day phenomenon is based off of the ratio of rotations of the Earth around its axis to the Earth's revolutions around the sun. It is a purely coincidental event. It was determined by the simple method of counting how many times the sun rose before a star reached the same point in the sky. 2) Earth's rotations reflect age simply because both take place over time. If we didn't use the Earth's rotation to measure time, we would find something else to relate it to. Since the cycle of day and night are observeable anywhere on the planet's surface (where the clear majority of the human race lives) it is much more conveinient to use than tides or daily events.

Answer 4

because it takes 365 1/4 days for the earth to finish one trip around the world. That is why every fourth year we have a leap year of 366 days to make up for the 1/4th of a day we lose every year.

Good Luck!!!

Answer 5

A year has 365 days because that's how long it takes for earth to revolve around the sun.

Answer 6

A question without a simple answer. See Wikipedia, the free, online encyclopedia for a complete explanation at:
http://en.wikipedia.org/wiki/Year

Here is a quote from thtat web page:

Calendar year
A calendar year is the time between two dates with the same name in a calendar.Solar calendars usually aim to predict the seasons, but because the length of individual seasonal years varies significantly, they instead use an astronomical year as a surrogate. For example, the ancient Egyptians used the heliacal rising of Sirius to predict the flooding of the Nile.

The Gregorian calendar aims to keep the vernal equinox on or close to March 21; hence it follows the vernal equinox year. The average length of its year is 365.2425 days.

Among solar calendars in wide use today, the Persian calendar is one of the most precise. Rather than being based on numerical rules, the Persian year begins on the day (for the time zone of Tehran) on which the vernal equinox actually falls, as determined by precise astronomical computations.

No astronomical year has an integer number of days or lunar months, so any calendar that follows an astronomical year must have a system of intercalation such as leap years.

In the Julian calendar, the average length of a year was 365.25 days. This is still used as a convenient time unit in astronomy."

Hope this helps!

Answer 7

This is the time it takes for the earth to make one circle around the sun.. every 4 years an additional "leap day" is needed to keep the calender working correctly. This is why every 4th year February has a 29th day.

Answer 8

b cuz that's how long it takes the world to go around the sun plus 1/4 of a day that's y we have a leap year every four years that is 366 days

Answer 9

the period of revolution of the Moon around the Earth (from full moon to full moon) is 29.53 days.

the period of revolution of Earth around the Sun is 365.24 days;

there are 12.37 lunar months in a year.