Why the Sun Sets Later After Daylight Saving Time Starts

Daylight Saving Time often confuses many people about the behavior of the sunset. You might wonder, "If Daylight Saving Time makes us jump only one hour, why does the sun set at least two hours later?" This article will address this common confusion and provide a clear explanation.

Understanding the Mechanics

Daylight Saving Time (DST) is implemented to make better use of daylight during the longer summer days. When we "spring forward" by one hour, our clocks go ahead, but this doesn't affect the sun's behavior. The sun's position in the sky is determined by its orbit around the Earth and the Earth's rotating position relative to the sun. Therefore, the sunset's timing is not controlled by the clock.

What does change? When the clocks adjust for DST, we switch to a time that seems to reflect a later sunset, even though the sun actually sets at the same time. The apparent later sunset is due to the fact that we have gained an hour of daylight in the evening.

Seasonal Impact on Sunset Timing

During the summer, the Earth's axial tilt causes the sun to stay up longer than during the winter. This means that the sun sets later each day, even without DST. By the time we reach the summer solstice, which is typically on June 21st, the sun will set as late as 9 PM or 9:15 PM (depending on your location).

Once spring's light-benefiting benefits have passed, the diminishing return sets in, and the shortening of the day begins. By the time we reach the winter solstice, which usually occurs on December 21st, the sun will set as early as 4:30 PM or 5:15 PM.

So, why does the sun seem to set at least a couple of hours later after DST begins? The answer lies in the gradual nature of the change in sunset times due to the Earth's axial tilt and the shorter duration of daylight. Let's break this down with some specific examples.

Regional Variations in Sunset Timing

In large metropolitan areas like Portland, Oregon (USA), the length of day is increasing significantly by the time DST begins. On the last day before DST, the city experienced civil twilight starting at 18:07. Just one month later, on April 23rd, civil twilight would start at 20:07. This change is not solely due to DST; rather, it's a combination of the early spring and DST’s one-hour adjustment.

For cities with more extreme northern latitudes, like Fairbanks, Alaska, the day length changes more drastically. Before the transition to DST, civil twilight started at 18:32 on March 8th, 2019, and by April 16th it would start at 21:31. Again, it's important to note that DST accounts for only one hour of this longer twilight period.

Each day, the sunset time changes minimally due to the Earth's axial tilt. During the spring, this change is more pronounced as the days grow longer. The actual sunset time depends on your exact latitude and longitude, so these changes can vary based on your location.

Conclusion

Daylight Saving Time does not change the time the sun sets. Instead, it adjusts our clocks to reflect the longer summer days. The sun sets later because the days are longer, both before and after DST. Understanding these natural cycles can help us better appreciate the beauty of the seasons and the workings of our planet.