Solstice

Today is the longest day in the year.

UT date and time of equinoxes and solstices on Earth[1]
event	equinox		solstice		equinox		solstice
month	March		June		September		December
year
	day	time	day	time	day	time	day	time
2010	20	17:32	21	11:28	23	03:09	21	23:38
2011	20	23:21	21	17:16	23	09:04	22	05:30
2012	20	05:14	20	23:09	22	14:49	21	11:12
2013	20	11:02	21	05:04	22	20:44	21	17:11
2014	20	16:57	21	10:51	23	02:29	21	23:03
2015	20	22:45	21	16:38	23	08:21	22	04:48
2016	20	04:30	20	22:34	22	14:21	21	10:44
2017	20	10:28	21	04:24	22	20:02	21	16:28
2018	20	16:15	21	10:07	23	01:54	21	22:23
2019	20	21:58	21	15:54	23	07:50	22	04:19
2020	20	03:50	20	21:44	22	13:31	21	10:02

The Solstice occurs twice each year (around June 21 and December 22) as the Sun reaches its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. The seasons of the year are directly connected to both the solstices and the equinoxes.

Sunset

Sunset

The term solstice can also be used in a broader sense, as the day when this occurs. The day of the solstice has either the most sunlight of the year (summer solstice) or the least sunlight of the year (winter solstice) for any place other than the equator. Alternative terms, with no ambiguity as to which hemisphere is the context, are June solstice and December solstice, referring to the months of year in which they take place.

Sunrise

Sunrise

At latitudes outside the tropics, the summer solstice marks the day when the sun appears highest in the sky.
The word solstice is derived from the Latin sol (sun) and sistere (to stand still), because at the solstices, the Sun stands still in declination; that is, the seasonal movement of the Sun's path (as seen from Earth) comes to a stop before reversing direction.