DateKeep

About the Solar Calendar

The Solar Calendar tool offers a detailed look at the Earth's relationship with the Sun. It provides a visualization of the daily cycle of light—from the deep of night, through the various stages of twilight, to full daylight, and back again. This tool also highlights the key astronomical events that define our seasons: the solstices and equinoxes.

Visualizing the Day

The timeline at the top of the tool shows a 24-hour period for your location, broken down into distinct phases:

• Night: When the sun is more than 18 degrees below the horizon.
• Astronomical Twilight: When the sun is between 12 and 18 degrees below the horizon. The sky is dark enough for astronomical observation.
• Nautical Twilight: When the sun is between 6 and 12 degrees below the horizon. The horizon is visible, which was critical for historical sea navigation.
• Civil Twilight: When the sun is less than 6 degrees below the horizon. There is enough natural light for most outdoor activities without artificial light.
• Daylight: The period between sunrise and sunset.

Solstices and Equinoxes

These four events mark the astronomical beginning of the seasons. The calculator lists the upcoming dates and times for these key moments in the Earth's orbit, allowing you to see exactly when the seasons change.

Related Tools

While this tool focuses on the Sun, you can explore the cycles of the Moon with our Lunar Calendar. To find the day of the week for any date, use the Weekday Calculator.