NASA's water cycle research missions can be grouped into 3 major categories; Water Cycle, Energy Cycle, and Water and Energy Cycle Missions. By studying each and every variable of Earth's water and energy cycles, As Only NASA Can, a crucial understanding of the water cycle's effect on global climate is currently underway.
Home > Holiday and Occasions > Fall - Autumn > When is the first day of Fall - Autumn 2017? When is the first day of fall 2017? In 2017, fall begins on September 22rd (at 20:02 UTC) for countries in the Northern Hemisphere. The date may be different for you based on what time zone you live in. This chart reflects the UTC time zone. Note: Equinoxes are opposite on each side of the equator.
At a certain point, because of Earth's tilt, the days and nights become exactly the same length and that point is the exact start of spring (or fall - the exact opposite point in the orbit 6 months later). When the orbit reaches the point with the longest day, that's the start of summer. The point with the shortest day is exactly half way around, 6 months later and is the start of winter.