The March equinox happened on 20 March at 04:30 UTC.
By Jose Prieto (EUMETSAT)
This event in 2016 continues its shift towards an earlier time in our official calendar on leap years. It is now the earliest in the year since 1896. This trend will only be broken in 2100, because it will not be a leap year, thus delaying its occurrence by almost one day.
Equinox literally means 'equal night' (equi - equal and nox - night), basically the date of equal length of night and day. The actual length of daylight on 20 March is about ten minutes longer than 12 hours, due to atmospheric refraction. In the Northern Hemisphere it's known as the Vernal (Spring) equinox and it's the Autumnal (Fall) equinox in the Southern Hemisphere.
The Sun crosses the celestial equator from south to north, so it falls perpendicular on the Earth's equator, as can be noticed in the strong sun glint on the Indian Ocean in the Natural Colour RGB at 04:30 UTC (Figure 1).
Meteosat-10 Natural Colour RGB, 20 March 12:00 UTC
Himawari-8 Geocolour, 20 March 04:30 UTC (Source: CIRA)
GOES-15 Visible, 20 March 19:30 UTC (CIMSS Blog)
The first day of spring. The Vernal Equinox: Everything you need to know (The Telegraph)