JUNE 21, 2011* - First Day of Summer (Solstice)
The First Day of Summer (sumardagurinn fyrsti) is an annual public holiday in Iceland held on the first Thursday after April 18. In former times, the Icelanders used the Old Norse calendar which divided the year into only two seasons, winter and summer. Although the climate in late April cannot be considered to be summer-like, after the long winter, Icelanders still celebrate this first day of "summer" with parades, sporting events and organized entertainment, held in various places around Iceland.
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the Sun being vertically above a point on the Equator. The term equinox can also be used in a broader sense, meaning the date when such a passage happens. The name "equinox" is derived from the Latin aequus (equal) and nox (night), because around the equinox, the night and day are approximately equally long. It may be better understood to mean that latitudes +L and -L north and south of the equator experience nights of equal length.
The word is also used for the same event happening on other planets and in setting up a celestial coordinate system; see equinox (celestial coordinates).
At an equinox, the Sun is at one of two opposite points on the celestial sphere where the celestial equator (i.e. declination 0) and ecliptic intersect. These points of intersection are called equinoctial points: the vernal point and the autumnal point. By extension, the term equinox may denote an equinoctial point.
An equinox happens each year at two specific moments in time (rather than two whole days), when there is a location on the Earth's Equator where the centre of the Sun can be observed to be vertically overhead, occurring around March 20/21 and September 22/23 each year.
From Wikipedia, the free encyclopedia
*The 1st day of Summer will be as follows:
2011 – June 21
2012 – June 20
2013– June 21
2014 – June 21