Dawn Calculator — Free Online Civil, Nautical & Astronomical Dawn Tool

How to Use the Dawn Calculator

1. Select a city or enter coordinates: Choose from 10 global city presets including New York, London, Tokyo, and more. Each preset automatically fills the latitude and longitude fields. For any other location, enter custom coordinates. Latitude ranges from -90 to 90 degrees, and longitude from -180 to 180 degrees. You can find coordinates for any location using online map services.
2. Choose your date: Select the date for the dawn calculation. The default is today. Try different dates throughout the year to see how dawn times shift with the seasons. The seasonal variation is most dramatic at higher latitudes.
3. Read the dawn progression: The results panel displays all four key morning events in chronological order from darkest to brightest: astronomical dawn (-18°), nautical dawn (-12°), civil dawn (-6°), and sunrise (0°). Each event is shown with both UTC time and approximate local time. The visual design progresses from dark to light, representing the natural brightening sequence.
4. Review time between phases: The information panel at the bottom shows the exact number of minutes between each consecutive dawn phase. This helps you understand how quickly the sky brightens at your location and plan activities that require specific light conditions.

Compare dawn times across seasons to understand the full range of variation at your location. At the equator, dawn phases maintain consistent timing year-round. At high latitudes, summer dawn can begin many hours before sunrise, while winter dawn phases are compressed into a shorter window.

Dawn Calculation Formula

Variables Explained

• Altitude: The threshold angle below the horizon that defines each dawn type. Civil dawn uses -6 degrees, nautical dawn uses -12 degrees, and astronomical dawn uses -18 degrees. These are internationally standardized values used by navigational and astronomical authorities worldwide.
• Latitude (lat): Your north-south position on Earth. Latitude strongly influences the duration and separation of dawn phases. Higher latitudes experience longer, more drawn-out dawn progression, while equatorial locations have shorter, faster transitions.
• Solar Declination (dec): The Sun's angular position relative to the celestial equator, ranging from +23.44° to -23.44° throughout the year. This drives the seasonal variation in dawn times.
• Hour Angle: The angular distance between solar noon and the dawn event. Different altitude thresholds produce different hour angles, yielding the three distinct dawn times. Larger altitude thresholds (like -18°) produce larger hour angles and earlier dawn times.
• Solar Noon: The reference point from which dawn times are calculated by subtracting the hour angle. Solar noon is determined by the date, longitude, and the equation of time.

Step-by-Step Example

Calculate the three dawn times for London (51.5074° N, 0.1278° W) on December 21, 2026 (winter solstice):

1. Solar declination at winter solstice: approximately -23.44 degrees
2. Calculate hour angle for each altitude threshold with latitude 51.5074°
3. For civil dawn (-6°): hour angle gives time approximately 07:20 UTC
4. For nautical dawn (-12°): hour angle gives time approximately 06:36 UTC
5. For astronomical dawn (-18°): hour angle gives time approximately 05:51 UTC
6. Sunrise at -0.833° threshold: approximately 08:04 UTC
7. Time from astronomical dawn to sunrise: approximately 2 hours 13 minutes

On the winter solstice in London, the entire dawn progression spans over 2 hours, with each phase lasting approximately 40-45 minutes. This is considerably longer than at equatorial locations where the total dawn duration is about 70-80 minutes.

Practical Examples

Example 1: Omar's Ramadan Suhoor Timing

Omar lives in Cairo (30.0444° N, 31.2357° E) and needs to complete his pre-dawn meal (Suhoor) before the Fajr prayer during Ramadan in March 2026. Different Islamic calculation methods reference different dawn types for Fajr. His local mosque uses the Egyptian General Authority method, which defines Fajr at 19.5 degrees below the horizon (close to astronomical dawn at -18°). Using the dawn calculator for March 10, 2026:

• Astronomical dawn (-18°): approximately 04:10 local time
• Nautical dawn (-12°): approximately 04:41 local time
• Civil dawn (-6°): approximately 05:11 local time
• Sunrise: approximately 05:37 local time

Omar sets his alarm for 03:30 to prepare and eat Suhoor, ensuring he finishes well before the Fajr time of approximately 04:10. He checks the dawn calculator every few days during Ramadan since the times shift by about 1-2 minutes daily as spring progresses and days lengthen. By the end of March, Fajr will be approximately 15 minutes earlier.

Example 2: Claire's Astrophotography Session

Claire is an astrophotographer in Los Angeles (34.0522° N, 118.2437° W) planning to photograph the Andromeda Galaxy on a clear November evening. She needs to know when to stop taking long-exposure images before dawn brightens the sky. Using the dawn calculator for November 15, 2026:

• Astronomical dawn (-18°): approximately 05:01 local time (PST)
• Nautical dawn (-12°): approximately 05:32 local time
• Civil dawn (-6°): approximately 06:02 local time
• Time between astronomical and nautical dawn: 31 minutes

Claire sets up her equipment in the evening and plans to end long-exposure imaging at 04:45 AM, about 15 minutes before astronomical dawn, to ensure her final images are not contaminated by sky glow. She uses the time between nautical and civil dawn (06:02 minus 05:32 = 30 minutes) for wide-angle twilight landscape shots where a brighter sky adds dramatic color to the eastern horizon.

Example 3: Lieutenant Chen's Maritime Navigation

Lieutenant Chen is navigating a cargo vessel through the Singapore Strait (1.3521° N, 103.8198° E) and needs to determine when nautical dawn begins for celestial navigation sightings. Nautical dawn is critical for marine navigation because it is the earliest time when the horizon is visible enough to take star sightings with a sextant while stars are still visible. Checking for February 15, 2026:

• Astronomical dawn (-18°): approximately 05:51 local time
• Nautical dawn (-12°): approximately 06:14 local time
• Civil dawn (-6°): approximately 06:37 local time
• Sunrise: approximately 06:58 local time

Lieutenant Chen plans star sights during the nautical twilight window from 06:14 to 06:37 when both the horizon and navigation stars are simultaneously visible. Near the equator in Singapore, dawn phases are consistent year-round (varying by less than 10 minutes across the year), which simplifies scheduling compared to higher-latitude routes where dawn timing varies dramatically by season.

Example 4: Sofia's Bird-Watching Expedition

Sofia is a birdwatcher visiting Tromso, Norway (69.65° N, 18.96° E) in late May to experience the midnight sun and the spring bird migration. She wants to understand the dawn situation at this extreme northern latitude. Checking the calculator for May 25, 2026:

• Astronomical dawn: does not occur (Sun never goes below -18°)
• Nautical dawn: does not occur (Sun never goes below -12°)
• Civil dawn: does not occur (Sun never goes below -6°)
• The Sun is above the horizon 24 hours (midnight sun)

Sofia discovers that at nearly 70° N in late May, there is no dawn at all because the Sun never sets. The entire 24-hour period has continuous daylight. This is ideal for bird-watching as migratory species are active throughout the extended daylight. She plans her most intensive observation periods during the low-Sun hours (between 23:00 and 03:00 local time) when the lighting creates beautiful conditions and many species are most vocal. For day-of-year tracking, the day of year calculator helps her log observation dates precisely.

Dawn Times Reference Table

Approximate local dawn times for selected dates. Times are in local standard time. N/A indicates the Sun does not reach that depth below the horizon.

Tips and Complete Guide

Understanding the Dawn Color Progression

As dawn progresses through its three phases, the sky undergoes a predictable color sequence. During astronomical dawn, the eastern horizon shows the faintest grey-blue lightening against the star-filled sky. During nautical dawn, a band of deep blue-violet develops along the eastern horizon, gradually expanding upward. The famous "blue hour" occurs during the transition from nautical to civil dawn, characterized by deep blue tones across the sky. During civil dawn, warm colors (pink, orange, gold) appear along the horizon as scattered sunlight grows stronger. Understanding this color progression helps photographers and sky watchers plan for specific conditions.

Dawn at Different Latitudes

The latitude of your location dramatically affects dawn characteristics. At the equator, the Sun rises nearly vertically, so each dawn phase lasts only about 20 minutes and the total time from astronomical dawn to sunrise is roughly 60-70 minutes. At temperate latitudes (40-50 degrees), each phase lasts 25-35 minutes, totaling about 90-120 minutes. At arctic latitudes during certain seasons, the dawn progression can last many hours because the Sun approaches the horizon at a very shallow angle. In June at latitude 60° N, civil dawn begins around 2:00 AM while sunrise may not occur until 4:00 AM, creating a 2-hour civil twilight period.

Practical Uses of Dawn Data

Dawn time data serves numerous practical purposes beyond the obvious. Farmers use civil dawn to plan early morning harvesting when temperatures are coolest. Military operations historically used nautical dawn (referred to as BMNT — Begin Morning Nautical Twilight) for tactical planning, as troops could move but were difficult to spot. Airport operations reference civil dawn for determining when visual flight rules (VFR) conditions begin. Construction sites often cannot begin noise-generating work until after civil dawn in residential areas. Wildlife researchers use dawn phases to time surveys for species that are most active during specific twilight conditions.

White Nights and Polar Twilight

At latitudes above approximately 48.5° N or S, there are periods in summer when the Sun never drops below -18 degrees, meaning astronomical darkness never occurs. This creates "white nights" where the sky retains some illumination all night. At higher latitudes, nautical darkness (-12°) and eventually civil darkness (-6°) also fail to occur. The most famous example is St. Petersburg, Russia (59.9° N), where white nights occur from late May through mid-July. At Tromso, Norway (69.7° N), the midnight sun means the Sun does not set at all from May 20 to July 22. Conversely, during polar winter, some or all dawn phases may be absent for weeks or months.

Common Mistakes to Avoid

• Confusing civil dawn with sunrise: Civil dawn occurs 20-35 minutes before sunrise. If you need to be somewhere at sunrise, arriving at civil dawn means you will have a significant wait. Conversely, if you only need ambient light (not direct sunlight), civil dawn is sufficient.
• Using the wrong dawn type for religious observances: Different religious authorities may reference different dawn types or even intermediate angles (like -15° or -19.5°) for prayer times. Always verify which specific solar angle your religious authority uses rather than assuming one of the three standard dawn types.
• Ignoring seasonal variation at high latitudes: At latitudes above 45 degrees, dawn times can shift by over an hour between adjacent months near the solstices. Always check times for your specific date rather than relying on remembered times from a different season.
• Expecting consistent dawn duration: The time between dawn phases is not fixed. Near the equinoxes, each phase is relatively uniform. Near the solstices at high latitudes, the phases stretch significantly, with the total dawn period lasting much longer than at other times of year.
• Forgetting about terrain and buildings: The calculator assumes a flat, unobstructed eastern horizon. Mountains, buildings, or other obstructions to the east delay the perceived brightening even though the astronomical calculations remain accurate for the geometric position of the Sun.

Frequently Asked Questions