This year's summer solstice, which normally falls on 21 June, arrives a day earlier today to delight astronomy lovers.
David Moore, editor of Astronomy Ireland magazine, said this year's solstice is the earliest it has happened in more than 325 years.
"This one is a bit of a record because it is the earliest that it has happened, 20 June 9.50pm tonight, since 1796."
Read More: Summer Solstice: the longest day and shortest night of the year
Speaking on RTÉ’s News at One, Mr Moore explained why it has come early this year.
"The earth is going around the sun every year, and the year isn’t an exact number of days. It is 365 and a quarter days long, roughly speaking. So, we have to reset our calendar every four years with a leap day at the end of February."
He said this resets the exact moment we reach the solstice, adding that this is the start of summer in the Northern Hemisphere.
"Because what is happening is the earth's axis is tilted directly toward the sun, the closest it can get pointing toward the sun."
