Welcome to the beginning of fall, defined by the autumnal equinox (in the northern hemisphere) or the southward equinox (hemisphere-neutral).
On the day of the equinox, the Sun appears to rise “due east” and set “due west”. In Denver, the equinox this year occurs at 7:03:34 pm MDT on September 22, 2022.
Vernal equinox and autumnal equinox: these classical names are direct derivatives of Latin (ver = spring, and autumnus = autumn). These are the historically universal and still most widely used terms for the equinoxes, but are potentially confusing because in the southern hemisphere the vernal equinox does not occur in spring and the autumnal equinox does not occur in autumn. The equivalent common language English terms spring equinox and autumn (or fall) equinox are even more ambiguous. It has become increasingly common for people to refer to the September equinox in the southern hemisphere as the Vernal equinox. Confusing!
To avoid confusion use northward equinox and southward equinox, names referring to the apparent direction of motion of the Sun. The northward equinox occurs in March when the Sun crosses the equator from south to north, and the southward equinox occurs in September when the Sun crosses the equator from north to south.
Welcome to Fall in Denver! Just remember, winter is coming, otherwise known at the December solstice, also known as the southern solstice on December 21 (in Denver).