Which month has 12 hrs of daylight each day?

Answer 1

Exactly 12 or at least 12?

Exactly 12: March and September
At least 12: March through September

Answer 2

There is no such thing.

There are two DAYS in the year at which we say that the day is equal to the night. These are the equinoxes (not the solstices) and they fall around March 20th and September 23rd of each year. In reality, though, this is an approximation.

The Sun is not a point source. On the equinoix, the CENTER of the Sun is above and below the horizon for half of the day each, but the Sun is a disk. Even if the center of the Sun is below the horizon, the upper edge is 1 degree away. The Sun moves one degree in 4 minutes, so the equinox really has 8 minutes more sunlight than dark (4 minutes at dawn and sunset).

Also, the atmosphere refracts, or bends, light. Even if the Sun is truly below the horizon, sunlight is still visible. This is why the Sun has a sort of oval shape as it rises and sets (but don't look without a filter). This adds more time to the day.

Answer 3

The cause of the seasons is that the rotation axis of the Earth is not perpendicular to its orbital plane, but makes an angle of about 23.44°, the obliquity of the ecliptic, and that this axis keeps its orientation in inertial space. By consequence, for half a year (from around 20 March to around 22 September) the northern hemisphere tips toward the Sun, with the maximum around 21 June, while for the other half year the southern hemisphere has this honour, with the maximum around 21 December. The two instances that the Sun is overhead on the equator are the equinoxes. Also at that moment both the north pole and south pole of the Earth are just on the terminator, and therefore day and night are equally divided over the whole globe.

The table above gives the instances of equinoxes and solstices over several years. A few remarks can be made.

The actual equinox is a single moment in time — it does not take the whole day. But the crossing of the Sun over the equator is slow enough that the equinox day will have 12 hours of daylight and 12 hours of nighttime, and within an accuracy of a few minutes, the day before and after too.
It is 94 days from the June solstice to the September equinox, but only 89 days from the December solstice to the March equinox. The seasons are not of equal length because of the variable speed the Earth has in its orbit around the Sun.
The instances of the equinoxes are not fixed but fall about six hours later every year, amounting to one full day in four years, but then they are reset by the occurrence of a leap year. The Gregorian calendar is designed to follow the seasons as accurately as possible. It is good, but not perfect. Also see: Gregorian calendar#calendar seasonal error.
Smaller irregularities in the times are caused by perturbations of the Moon and the other planets.
Currently the most common equinox and solstice dates are 20 March, 21 June, 22 September and 21 December, the four year average slowly shifting to earlier times in the years to come. This shift is a full day in about 70 years (largely to be compensated by the century leap year rules of the Gregorian calendar). But that also means that as many years ago the dates of 21 March, 22 June, 23 September and 22 December were much more common, as older books teach and older people still remember.

Answer 4

If you lived on the equator, every day would be 12 hours long, so the answer would be every month; elsewhere on the planet, days are shorter than 12 hours in winter and longer than 12 hours in the summer; two months would have one day each where they are 12 hours, but no month would have nothing but 12 hour days.

Answer 5

I believe you're looking for the Summer solstice or June 21st.
On this day there is exactly 12 hours of day light and twelve hours of night! Then afterwards on the next day, of June 22nd, the day light is approximately two minutes shorter then on the previous day!