What time of year is day the same length as night?

Answer 1

The Autumnal and Vernal Equinoxes, occurring around March 21st and September 23rd, are the two days of a given year that day and night are equal in duration. This happens because contrary to popular belief, the sun does not rise and set directly overhead, or perpendicular to the horizon for most of the year. The path that the sun travels across the sky is not perfectly centered, except of course during the equinoxes. Because the sun is directly overhead at 12 o'clock noon during the equinox, if you were to travel to the equator, you would not cast a shadow.

Answer 2

The length of night is always equal to the length of night, regardless of the location
on Earth or the time of the year. In addition, the length of day is also equal to the
length of night, on two occasions in the year. If atmospheric effects are ignored,
the occasions are nominally the days of the Spring and Fall equinoxes, roughly
March 21 and September 21. If atmospheric effects are included, then the actual
dates are a few days before the March equinox and a few days after the September
one (in the northern hemisphere).

Answer 3

Approximately at the equinox. Note that this is not the exact definition of the equinox, and day and night are not exactly the same length at the equinox.