How to Calculate Daylight

As the earth revolves around the sun, a specific geographical location will experience fluctuating amounts of daylight throughout the year. Total daylight is defined as the amount of time between sunrise and sunset. You can, therefore, calculate the total daylight for a specific geographical location if you know the exact time of the sunrise and sunset on a specific calendar date.

Instructions

1. Determine the sunrise and sunset times for a specific location on a specific day. TimeAndDate.com, SunriseSunset.com and the U.S. Navy offer online tools you can use to find out the sunrise and sunset times. For example, on January 24, 2011, the sun rose at 7:27 a.m. and set at 5:52 p.m. in Dallas, Texas.

2. Calculate the number of complete hours of daylight. Convert the times to military time and subtract the sunrise time hour from the sunset time hour. Continuing the same example, on January 24, 17 - 7 = 10. There were 10 complete hours of daylight on this day.

3. Calculate the number of minutes for the final hour of daylight. Subtract the sunrise minutes from the sunset minutes. Continuing the same example, 52 - 27 = 25 minutes.

4. Add the hour figure from step 3 to the minute figure from step 2 to determine the hours of daylight for the specific day. Continuing the same example, 10 hours + 25 minutes = 10 hours and 25 minutes. There were 10 hours and 25 minutes of daylight in Dallas, Texas on January 24, 2011.

References

• Time and Date: sunrise and Sunset Calculator
• Sunrise Sunset: Location Selection for Sunrise Sunset Calendar
• Navy: Complete Sun and Moon Data for One Day