Julian Day Calculator and Date Converter

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Today's Julian Day Number is 2458651 GMT 2019 ?

Monday, June 17, 2019 AD at 03:33:00
JDN: 2458651.6479167

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Date and Moon Phase

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Graphical representation of selected Julian Day.

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Graphical Julian Day.
Ephemeris Data is displayed here.

Moon Phase, Julian Calculator and Date Converter

Use this calculator to convert between Julian or Gregorian calendar dates and a corresponding Julian Day Number. See the phase of the moon and the earth's orbital position for any date and time in the future or the past (A.D. or B.C.).

We number Julian days sequentially from Monday, January 1, 4713 B.C. using, coincidentally, the Julian calendar. Nearly 2-1/2 million days have passed since then.

Astronomers developed the system long ago to chronicle astronomical observations. Since observation usually occurred during the night, Julian Day Numbers (JDN) change during the day (at noon for convenience). Astronomers based the Julian Day Number system on a uniform time scale, but the earth's rotation varies very slightly and somewhat unpredictably. We measure the difference between the uniform Julian Day time and sundial time in seconds of difference. We call this difference, Delta-T, and its value is fairly insignificant unless we are looking far back in time or ahead in the future. For example, in our study of the Elephantine Papyri, written during the fifth-century B.C., delta-t is only a couple of hours, but a few hundred years earlier, it is several hours.

Our current Gregorian calendar is a slightly modified Julian calendar, which itself is a modified Egyptian calendar. We compared known Egyptian dates to reconstruct the calendar used by Daniel, Ezekiel, Ezra and Nehemiah from the double-dated, Elephantine Island papyri.

Our date calculator converts a Julian Day Number to a standard date in either the Julian or Gregorian dating systems. It also converts any date to a Julian Day Number. Convention dictates that after Pope Gregory's changes to Julius Caesar's calendar in 1582, we use the Gregorian Calendar for dating events. We use the proleptic Julian calendar for all dates between 1582 and the beginning of time. Nevertheless, this calculator provides an option to show the Julian calendar date (not to be confused with Julian Day Numbers) or the corresponding Gregorian calendar date for any date past, present, or future. The Julian and Gregorian systems vary only slightly; the average length of a Julian year is 365.25 days while the Gregorian year averages 365.2425 days, which is closer to the true, tropical year length of 365.242189 days.

We developed this Date Converter to thoroughly investigate Bible Chronology and the time prophecies of Daniel and Revelation.

World Map

The appearance of the moon changes slightly based on where the observer is located. The map offers a few scattered locations across the globe remembering that the time given is that of Greenwich, England.

Babylonian Dates are based on the work of Richard A. Parker and Waldo H. Dubberstein entited "Babylonian Chronology 620 B.C. - A.D. 75"

Julian Day and Moon Phase Calculator

Ephemeris for sun and moon data that displays the moon phase: Click on the menu below the illustration to see data.


This Calculator is a companion tool for the book:
Daniel's Calendar Decoded:
From the Elephantine Papyri