Blue Hour Time Calculator
Estimate the morning and evening blue-hour twilight windows — the deep-blue light just before sunrise and after sunset — from your local times.
How it works
evening blue hour = sunset + offset → + length · morning blue hour = sunrise − offset − length → sunrise − offset
Blue hour is the twilight just before sunrise and just after sunset, when the Sun is a few degrees below the horizon and the sky glows a deep, even blue. It follows the evening golden hour (and precedes the morning one), typically starting around 10 minutes after sunset and lasting 20 to 30 minutes. The exact timing depends on latitude and season, so treat the offset and length as adjustable to match how long the blue light holds where you are.
Worked example
With sunset at 7:30 PM, a 10-minute offset and a 20-minute window, evening blue hour runs about 7:40–8:00 PM; the morning version ends 10 minutes before a 6:30 AM sunrise, so roughly 6:00–6:20 AM.
Frequently asked questions
How is blue hour different from golden hour?
Golden hour is warm light while the Sun is just above the horizon; blue hour is the cooler twilight while the Sun is just below it. Blue hour follows golden hour in the evening and comes before it in the morning.
How long does blue hour last?
Usually 20 to 30 minutes at mid-latitudes, longer toward the poles and shorter near the equator. Adjust the length input to match your location and time of year.
Why the offset after sunset?
The best blue tones appear once the Sun is a few degrees below the horizon, which is a little after sunset rather than at the moment it drops. The offset shifts the window to that point.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.