As of 7:02 a.m. today, spring had officially arrived. The first day of spring, the vernal equinox, has 12 hours of daylight and 12 hours of darkness. After today, the length of daylight will increase until the first day of summer, the summer solstice, arrives. This year, summer will arrive at 1:04 a.m. on June 21st. After the first day of summer, the length of the day will again start to decrease.