Daylight Hours Calculator

Enter a date and latitude/longitude to calculate daylight hours, sunrise and sunset times, night duration, and solar declination for that location.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Enter the Date
Input the specific date (YYYY-MM-DD) for which you want to determine daylight hours.
2
Provide Latitude
Enter the latitude in decimal degrees. Positive for North, negative for South (range: -90 to 90).
3
Provide Longitude
Enter the longitude in decimal degrees. Positive for East, negative for West (range: -180 to 180).
4
Review Daylight Metrics
The calculator will display total daylight duration, sunrise/sunset times (UTC), night duration, solar declination, and the percentage of daylight in the day.

Example Calculation

A gardener in New York City (Latitude 40.7128°, Longitude -74.0060°) needs to know the daylight duration on April 25, 2026, to plan planting schedules.

Date

2026-04-25

Latitude

40.7128 °

Longitude

-74.0060 °

Results

13.67 hrs

Tips

Optimize Planting Schedules

Gardeners can use daylight hours to determine optimal planting and harvesting times for sun-loving versus shade-tolerant plants. Many vegetables require 6-8 hours of direct sun daily.

Plan for Energy Efficiency

Homeowners can use this data to understand natural light availability for passive solar heating or to schedule lighting usage, potentially reducing energy consumption during shorter daylight periods.

Understand Solar Panel Performance

For solar energy users, longer daylight hours generally correlate with higher solar panel output. Track this throughout the year to anticipate seasonal energy generation fluctuations.

Mastering Solar Cycles: Your Comprehensive Daylight Hours Calculator

The Daylight Hours Calculator offers a detailed analysis of sunlight availability for any date and location, providing crucial data on daylight duration, sunrise, sunset, and solar declination. This tool is invaluable for a wide range of applications, from urban planning and agriculture to personal scheduling and energy management. By accurately depicting how long the sun remains above the horizon, it helps users understand seasonal light variations and plan effectively, whether for garden planting in April 2026 or optimizing solar energy capture.

The Interplay of Earth's Tilt and Orbit

The variation in daylight hours throughout the year is a direct consequence of the Earth's axial tilt (approximately 23.5 degrees) and its orbit around the sun. As the Earth revolves, different hemispheres are tilted towards or away from the sun, leading to distinct seasons and fluctuating daylight durations. When the Northern Hemisphere is tilted towards the sun (summer solstice), it experiences longer days and shorter nights, while the Southern Hemisphere experiences the opposite. At the equinoxes, when neither hemisphere is tilted towards the sun, daylight and nighttime hours are nearly equal across the globe. This celestial dance is the fundamental driver of our planet's seasonal light cycles.

How to Calculate Daylight Duration

The Daylight Hours Calculator determines the duration of sunlight by employing astronomical formulas that take into account the Earth's tilt, its position in orbit, and your specific location's latitude and longitude. The core logic involves calculating the solar declination and the hour angle of the sun.

// Intermediate calculation for solar declination
Solar Declination (deg) = 23.45 × sin(toRad((360 / 365) × (Day of Year - 81)))

// Intermediate calculation for hour angle (H)
cos(H) = (sin(-0.0145 rad) - sin(Latitude) × sin(Declination)) / (cos(Latitude) × cos(Declination))

// Final Daylight Duration
Daylight Duration (hours) = (2 × H (in degrees)) / 15

The Latitude and Longitude specify your location, and the Date determines the Day of Year and thus the Solar Declination. This precise calculation yields the total hours the sun is above the horizon.

💡 Understanding seasonal changes in daylight helps with planning. For winter-specific operations, our Snowblower Clearing Rate Calculator can help estimate efficiency in snow removal.

Gauging Sunlight for an April Day: A Practical Example

Let's determine the daylight hours for April 25, 2026, in New York City (Latitude: 40.7128°, Longitude: -74.0060°).

Input: Date: 2026-04-25, Latitude: 40.7128°, Longitude: -74.0060°.
Solar Declination: For April 25, 2026, the solar declination is approximately +12.94°.
Hour Angle Calculation: Using the latitude and declination, the hour angle is computed to be about 102.50°.
Daylight Duration: Daylight Duration = (2 × 102.50°) / 15 = 13.666... hours This rounds to 13.67 hours.
Sunrise/Sunset (UTC): The calculator further derives the approximate UTC sunrise (09:42 AM) and sunset (11:24 PM) times based on longitude and the Equation of Time.

The primary result indicates 13.67 hours of daylight for this spring day in New York.

💡 Just as daylight varies seasonally, so does snowfall. To predict winter conditions, our Snowfall Accumulation Calculator can help estimate total snow depth.

Weather-Climate Benchmarks for Daylight Variation

Seasonal variations in daylight hours are a fundamental aspect of weather and climate. At the equator (0° latitude), daylight remains remarkably constant at approximately 12 hours year-round. Moving towards the poles, this constancy diminishes dramatically. At 40° latitude, like New York City, summer solstice (around June 21) brings over 15 hours of daylight, while winter solstice (around December 21) reduces it to less than 9 hours. Beyond the Arctic and Antarctic Circles (66.5° latitude), periods of 24-hour daylight (midnight sun) and 24-hour darkness (polar night) occur, lasting from days to months. These extreme variations drive distinct climate zones, influencing everything from vegetation growth to human activity patterns.

Understanding When Daylight Calculations May Be Less Precise

While highly accurate, the Daylight Hours Calculator relies on a simplified model and may encounter limitations in specific edge cases. For locations very close to the poles (within the polar circles), the concept of distinct sunrise and sunset can become ambiguous, leading to "no sunrise" or "no sunset" results during periods of midnight sun or polar night. Additionally, the calculation for "Sunrise (UTC)" and "Sunset (UTC)" uses an approximate Equation of Time, meaning actual local times can vary by a few minutes due to atmospheric conditions, terrain (e.g., mountains blocking the horizon), and the precise definition of sunrise/sunset (first light vs. sun's center). For extreme precision in specialized applications like astronomy or navigation, more complex ephemeris data and local observations are often required.

Frequently Asked Questions

How does latitude primarily influence daylight duration?

Latitude is the most significant factor determining daylight duration because it dictates how directly the sun's rays hit a location as the Earth rotates on its tilted axis. At the equator (0° latitude), daylight hours are consistently around 12 hours year-round. As you move towards the poles (90° latitude), seasonal variations become extreme, leading to periods of 24-hour daylight (midnight sun) in summer and 24-hour darkness (polar night) in winter. The Earth's axial tilt of 23.5 degrees is key.

What is solar declination and why is it important?

Solar declination is the angle between the sun's rays and the plane of the Earth's equator. It varies throughout the year, ranging from approximately +23.45 degrees (summer solstice in the Northern Hemisphere) to -23.45 degrees (winter solstice). Solar declination is crucial because it determines the sun's apparent path across the sky and, consequently, the intensity and duration of sunlight received at different latitudes. It directly impacts seasons and daylight hours.

Does longitude affect the total length of daylight?

No, longitude does not affect the total length of daylight for a given date. Longitude primarily influences the *local clock time* of sunrise, sunset, and solar noon. Your longitude determines your position within a time zone, affecting when these events occur relative to a standardized clock. The total duration of daylight, however, is determined by your latitude and the date, due to the Earth's axial tilt and orbital position around the sun.