Daylight Hours in Nevada

Las Vegas runs from 14h 37m of daylight on June 21 down to 9h 42m on December 21, a difference of 4h 55m across the year. That single number is almost entirely a latitude fact, and it puts Nevada 36th of the fifty states for how much its day length moves.

The curve above is drawn from a real day by day calculation rather than from a smooth wave, which is why the two most useful marks on it are not where people expect. The earliest sunset falls on December 5, roughly two weeks before the shortest day, and the latest sunrise on January 6, roughly two weeks after it. Solar noon drifts later through the winter, which drags the whole day later against the clock while the day itself is still shortening. The evening end loses that race first and wins it back first, so the afternoons start drawing out well before the solstice while the mornings keep getting darker.

A time zone is an hour of real solar time wide, so two places on the same clock can be nearly an hour apart in what the sun is actually doing. Las Vegas sits 5 degrees east of the meridian Pacific time is built around, which puts solar noon about 19 minutes before clock noon and shifts every sunrise and sunset in Nevada earlier than the same latitude would give on the western side of the zone. On top of that, Nevada moves its clocks: PST in winter, PDT from the second Sunday in March to the first Sunday in November.

Civil twilight is the reason a sunset time is not the same as the end of the day. In Las Vegas on the longest day of the year the sun sets at 8:01 PM and civil twilight runs on until 8:32 PM, another 30 minutes of usable light. On the shortest day the same gap is only 29 minutes, because the sun is dropping toward the horizon at a steeper angle in winter than in summer.