Spring officially begins today at 12:57 PM EDT (16:57 UTC). Equinoxes occur twice a year, in March and September. When these events happen, the sun shines directly on the equator and the length of day and night are nearly the same. However below the equator the season flips so it is the beginning of autumn in Sydney, Australia. The first full day of spring (or autumn) will be 21 Mar 2014.