The VRT’s weatherman Frank Deboosere told VRT news that although we learn at school that the longest day is on 21 June, in Belgium the longest day can fall on either 20 or 21 June.
The astrological summer begins when the sun is directly above the Tropic of Cancer. The timing of the summer solstice can be timed to within a fraction of a second and can occur either during the day or during the night.
0.3 second’s difference
This year the astrological summer starts on 21 June at 0h34. The sun will set at 10pm sharp this evening and will rise at 4:43am tomorrow morning, making tonight the shortest night of the year and today the longest day in 2016.
However, 20 June is just 0.3 seconds longer than 21 June and weather conditions could even ensure that there is fractionally more daylight on 21 June.