The Julian Day Almanac
Professional astronomical date conversion and analysis. Gregorian, Julian Day Number, Modified Julian Date, Unix timestamp, moon phase, zodiac, solar declination, equation of time, and more. Built on the Fliegel‑Van Flandern algorithm for full proleptic Gregorian calendar support.
Enter a date
Enter a Julian value
Astronomical & calendar details
Add or subtract days
Days between two dates
Settings
Conversion log
Conversions you run will appear here so you can compare them.
Julian Day Numbers use the Fliegel & Van Flandern algorithm across the proleptic Gregorian calendar. Julian calendar (old style) and moon phase figures are approximate for dates far from the present. Equation of time and solar declination are computed using standard approximations. ΔT (Terrestrial Time − UT) is estimated from a simple polynomial. v5.0 Ultimate — Free forever, built with precision astronomy algorithms.
Why Choose Our Julian Date Converter 2026?
Our Julian Date Converter 2026 is a fast, accurate, and completely free online tool to convert Gregorian dates into Julian Day Number (JDN) and Modified Julian Date (MJD). Perfect for students, engineers, astronomers, and scientific calculations.
| Feature | BrooklynClick Tool | Other Tools |
|---|---|---|
| Free Access | ✅ Unlimited | ⚠️ Limited |
| MJD Support | ✅ Included | ❌ Not Available |
| Accuracy | ✅ Astronomical Standard | ⚠️ Varies |
| Mobile Friendly | ✅ Fully Responsive | ⚠️ Inconsistent |
| Instant Results | ✅ Yes | ⚠️ Slower |