They're the same length on either side of the date of the equinox, which falls in March and September. In 2009 those dates were 3/20 and 9/22, respectively. Just count days on either side of those dates, to answer our question.
What ends up happening, is that the first 20 days of March will have roughly the same length of daylight as the 20 days AFTER the September equinox (i.e. 9/22 thru 10/11). Similarly, the first twenty days of September will have the quality of daylight shown for the first 20 days after the spring equinox (3/20 thru 4/9)
In 2012, the day when spring and fall had roughly equal hours of daylight and darkness was the equinox on September 22nd. On this day, the lengths of day and night are approximately equal all around the world.
At the equinoxes, day and night are roughly equal in length at all latitudes. During the summer solstice in the Northern Hemisphere, there are long daylight hours and short darkness hours, while in the Southern Hemisphere it experiences the opposite. The winter solstice is reversed, with longer darkness hours in the Northern Hemisphere and longer daylight hours in the Southern Hemisphere.
On a solstice, it is only at the equator that the hours of light and dark are equal. At other parts, they would be different with one of the Poles experiencing 24 hours of daylight and the other Pole experiencing no daylight. If it is the June solstice, then it is the North Pole with 24 hours of daylight and the South Pole with none, while it is the opposite in the December solstice. It is at the equinox that the amount of daylight and darkness hours are equal around the world.
On June 21, the summer solstice, all points along the equator experience approximately 12 hours of daylight and 12 hours of darkness due to the tilt of the Earth's axis. This is the only day of the year when the entire equator receives an equal amount of daylight.
At the two equinoxes (about 22 September and 20 March).
I'm guessing march?
No. At an equinox, which happens in March and September, the amount of daylight and darkness are about equal.
March equinox and September equinox : Daylight and darkness are of equal length on both the Vernal Point (Spring/March 20th 2011) and the Autumnal Point (Autumn/September 23rd 2011) .
These are the spring and autumn equinoxes, and are days when the daylight and darkness are equal.
The northern and southern hemispheres have equal daylight and darkness on the equinoxes, which occur around March 21st and September 23rd each year. These are known as the spring (vernal) and autumnal equinoxes, respectively.
The northern and southern hemispheres have equal hours of daylight and darkness during the equinoxes, which occur around March 20-21 and September 22-23 each year.
As it is the month of an equinox, there is a fairly equal amount of darkness and light, so about 12 hours of daylight.
In 2012, the day when spring and fall had roughly equal hours of daylight and darkness was the equinox on September 22nd. On this day, the lengths of day and night are approximately equal all around the world.
The day when the number of daylight hours is equal to the number of darkness hours is known as the equinox. This occurs twice a year, usually around March 20th and September 22nd. At these times, the Earth's axis is not tilted towards or away from the sun, resulting in almost equal day and night.
Equinox
The duration of day and night is equal at the equator twice a year during the equinoxes in March and September. This phenomenon occurs because the Sun is directly above the equator, resulting in 12 hours of daylight and 12 hours of darkness.
The equinox is when day and night are of equal length (about 22 September and 20 March).