Time & Astronomy

Clocks are a human invention, but the thing they were built to track is not. This section covers the events in the sky that the calendar is derived from, and the arithmetic that turns an event published in UTC into a time on your own clock.

Solstices and Equinoxes Explained and Sunrise, Sunset and Twilight Explained deal with what decides how long your day is and when it begins. The eclipse guides, from the basic geometry through solar and lunar eclipses to why they do not happen every month, cover the events people plan trips around. Finally, How Astronomical Events Are Converted to Local Time is the practical one: these times are always published in UTC, and converting them is exactly where daylight saving trips people up.

Guides in this section (8)

What Is an Eclipse? The geometry that lines up three bodies, and why a solar eclipse and a lunar eclipse are nothing like the same event.
Solar Eclipse Explained Total, partial and annular eclipses, what changes on the ground during each, and why the path of totality is so narrow.
Lunar Eclipse Explained Why the eclipsed Moon turns red rather than going dark, how long it lasts, and why half the planet can watch the same one.
Why Don't Eclipses Happen Every Month? The Moon's orbit is tilted, so the shadows usually miss. What has to line up before an eclipse is possible at all.
Solstices and Equinoxes Explained The four moments that anchor the seasons, why each is an instant rather than a day, and how that instant reaches your calendar.
Sunrise, Sunset and Twilight Explained Where the official definitions come from, the three grades of twilight, and why day length behaves so differently by latitude.
Moon Phases Explained The 29.5-day cycle, what each phase actually shows you, and why the same phase falls at different local times around the world.
How Astronomical Events Are Converted to Local Time Astronomical events are published in UTC. This is how to turn one into the time on your own clock, daylight saving included.

Other guide sections

This is one of 8 sections in the library. The others cover Time Zones, Daylight Saving Time (DST), Business & Remote Work, Travel, Interesting Facts, City Comparison and Country Guides. The guides index lists every article we have published in one place.