The first day of spring (March equinox or vernal equinox) is when the sun shines directly on the celestial equator passing from south to north and the length of day and night are almost the same. This is referred to as astronomical spring or the March equinox or vernal equinox.

Astronomical spring starts at different times around the planet because of the different time zones as related to Coordinated Universal Time (UTC, same as Greenwich Mean Time based on the Royal Observatory in Greenwich, London [1]). For countries located west of UTC your spring will start earlier than countries located east of UTC.