Julian Day Calculations allow you to figure out the day of the week.
|Specify E or W
1 - East
2 - West
(12 hour UT)
Meeus, J. (1991). Astronomical algorithms. Richmond, Virginia USA, Willmann-Bell Inc., pages 60-65
timeprophecy.com - makes a nice detailed calculation of JD, Day of Week, Moonrise, Moonset, Sunrise, Sunset, etc. and is seamlessly valid for Julian and Gregorian calendar time periods
fourmilab computes JD - fourmilab computes Julian Day at UT zero hour (not 12). It has seperate entry forms for the Julian and Gregorian Calendars.
The Julian Day number or, more simply, the Julian Day (JD) is a continuous count of days and fractions thereof from the beginning of the year —4712. By tradition, the Julian Day begins at Greenwich mean noon, that is, at 12h Universal Time. If the JD corresponds to an instant measured in the uniform scale of Dynamical Time, the expression Julian Ephemeris Day (JDE) is often used. For example,
1977 April 26.4 UT = JD 2443 259.9In the methods described below, the Gregorian calendar reform is taken into account. Thus, the day following 1582 October 4 (Julian calendar) is 1582 October 15 (Gregorian calendar).
1977 April 26.4 TD = JDE 2443 259.9
The Gregorian calendar was not at once officially adopted by all countries. This should be kept in mind when making historical research. In Great Britain, for instance, the change was made as late as in 1752, and in Turkey not before 1927.
There is a disagreement between astronomers and historians about how to count the years preceding the year 1. In this book, the "B.C." years are counted astronomically. Thus, the year before the year +1 is the year zero, and -the year preceding the latter is the year —1. The year which the historians call 585 B.C. is actually the year —584. (Do not use the mention "B.C." when using negative years! " —584 B.C.", for instance, is incorrect.) [JW: This is accounted for in the Calculator so one should enter historical years]
The astronomical counting of the negative years is the only one suitable for arithmetical purposes. For example, in the historical practice of counting, the rule of divisibility by 4 revealing the Julian leap years no longer exists; these years are, indeed, 1, 5, 9, 13, ... B.C. In the astronomical sequence, however, these leap years are called 0, -4, -8, —12 , and the rule of divisibility by 4 subsists.
take care when using the INT function for negative numbers.
The week was not modified in any way by the Gregorian reform of the Julian calendar. Thus, in 1582, Thursday October 4 was followed by Friday October 15.
When is a given year a leap year ?
In the Julian calendar, a year is a leap (or bissextile) year of 366 days if its numerical designation is divisible by 4. All other years are common years (365 days).
For instance, the years 900 and 1236 were bissextile years, while 750 and 1429 were common years.
The same rule holds in the Gregorian calendar, with the following exception : the centurial years that are not divisible by 400, such as 1700, 1800, 1900, 2100, are common years. The other century years, which are divisible by 400, are leap years, for instance 1600, 2000, and 2400.
A.M. – Anno Mundi. This calendar was used by several of the Byzantine authors including Theophanes and Anastasius Bibliothecarius. The calendar is based on the Julian calendar however the year does not begin on 1 January and the starting day, month, and year of this calendar was a point of contention as it was based on an estimate for the start of "creation" (among other things) as interpreted through the Septuagint - a Greek translation of the Old Testament. An ongoing several hundred year long theological debate over when Biblical "creation" began led to multiple versions of the A.M. calendar. The earlier Byzantine sources used the Alexandrian version (A.M.a) or “Alexandrian era” of this calendar which has a starting date of 25 March 5492 BCE or, according to Bickerman (1980), 25 March 5493 BCE. Earthquake catalogers Guidoboni et al (1994) and Ambraseys (2009) assume a starting date of 25 March 5492 BCE and that is what I use. As explained by Grumel (1958:219)
The Alexandrian era of Panodorus began in 5493 BCE [and] the Alexandrian era of Annianos began in 5492 BCE. The Alexandrian Era of Annianos is what is commonly called the Alexandrian era.Another reckoning system, used for example by Megas Chronographos, is the Byzantine version (A.M.Byz) which has a starting date of 1 September 5509 BCE (Bickerman, 1980:73-74). Yet another reckoning system is a variant suggested in Chronicon Paschale which was composed in ~630 CE. The starting date for this system is 21 March, 5507 BCE. In the Anno Mundi calendar system used by the Byzantine authors, the day followed the Roman civil custom of beginning the calendarical day at midnight. When hours are indicated they mark time since dawn. Hence, if daybreak began at 6 am, the 4th hour would correspond to 10 am (Rautman, 2007:3).
|Theophanes||Theophanes used the Alexandrian version of the Anno Mundi calendar even though it was out of favor at the time and would be obsolete by the 9th century CE. He did so because his
Chronicle was a continuation of George Syncellus Chronicle which itself used the Alexandrian version of the Anno Mundi calendar. Proudfoot (1974:374)
noted that the
problem of whether Theophanes regarded the year as commencing on March 25 according to the Alexandrian world-year or on September 1 according to the Byzantine indiction cycle has not been resolved with  clarity.
Proudfoot (1974:373-374), and others have pointed out that Theophanes A.M.a
in the years A.M.a 6102-6206 and A.M.a 6218-6265 are frequently a year too low. The indictions, however, are
thought by many more likely to be correct.
The indiction runs from Sept. 1st, the Alexandrian A.M. from March 25th, but Theophanes probably dates the latter for calendar purposes from Sept. 1st2, to correspond with the Indiction.
Alexandrian fully QCed, Byzantine partly QCed and Chronicon Pachale not QCed
|Enter A.M. Year||Specify Reckoning
1 - Alexandrian
2 - Byzantine
3 - Chronicon Paschale
|Chosen Reckoning||Time Span in the Julian Calendar|
Indictions - An indiction (Latin: indictio, impost) was a periodic reassessment of taxation in the Roman Empire which took place every fifteen years.
In Late Antiquity, this 15-year cycle began to be used to date documents and it continued to be used for this purpose in Medieval Europe. Indictions
refer to an individual year in the 15 year cycle; for example, "the fourth indiction" came to mean the fourth year of the current indiction. Since
the cycles themselves were not numbered, other information is needed to identify the specific year. When an ancient author supplies an indiction along
with an A.M. date, the result may be greater chronological precision. For our dating purposes, indictions began in 312 CE when they were introduced by the Roman Emperor
Constantine. The indiction was first used to date documents unrelated to tax collection in the mid-fourth century.
By the late fourth century it was being used to date documents throughout the Mediterranean.
In 537 CE, Roman Emperor Justinian decreed that all dates must include the indiction.Outside of Egypt, the year of the indiction generally began on 1 September
|Input||Start Year (CE)||Notes|
|Invalid before 312 CE|
|Indiction||Year (CE)||Indiction Time Span outside of Egypt|
|Regnal Year||Start Day||Start Month||Start Year (CE)||Time Span in the Julian Calendar|
The Anno Graecorum (A.G.) Calendar is also known as the Seleucid Era, Chaldean, or the
This calendar began at the start of the Seleucid Empire and was
assimilated into the Babylonian calendar with Macedonian month-names sometimes substituted for the Babylonian names (Stern, 2012:238). The A.G. calendar uses the same
19 year cycle of intercalations as the Babylonian calendar. There are two start dates. The Macedonian reckoning used
by court officials in the Seleucid Empire and native Greek speakers started in the Autumn of 312 BCE with the start date eventually getting fixed
to 1 Oct. 312 BCE. The Babylonian reckoning used by most Semitic speaking populations has a start date of 1 Nisan in 311 BCE. Ambraseys (2009) equates this
to 1 April, Guidoboni et al (1994) equate this with 2 April, and others equate it to 3 April. A version of the A.G. calendar was used by the Christian Syriac authors such as Pseudo-Dionysius of Tell Mahre
and Chronicon Ad Annum 1234. Syriac writing authors would have likely used the
Macedonian reckoning as this was the standard usage among these authors for the Seleucid era (Sebastian Brock, personal communication, 2021 – see also Stern, 2012:236).
In the Anno Graecorum calendar system, the day starts at sundown (Sebastian Brock, personal communication, 2022).
|Macedonian Month||Julian Equivalent||Duration (days)|
|Xanthikos||22 March - 20 April||29|
|Artemisios||21 April - 20 May||30|
|Daisios||21 May - 19 June||29|
|Panemos||20 June - 19 July||30|
|Loos||20 July - 18 Aug.||29|
|Gorpiaios||19 Aug. - 17 Sept.||30|
|Hyperberetaios||18 Sept. - 17 Oct.||29|
|Dios||18 Oct. - 16 Nov.||30|
|Apellaios||17 Nov. - 16 Dec.||29|
|Audynaios||17 Dec. - 15 Jan.||30|
|Peritios||16 Jan. 14 Febr.||29|
|Dystros||15 Febr. - 16 March||30|
|Epagomenai||17 March - 21 March||5|
|Enter A.G. Year||Specify Reckoning
1 - Macedonian
2 - Babylonian
|Chosen Reckoning||Time Span in the Julian Calendar|
A.H. – Anno Hegirae is also known as the Muslim Calendar or the Islamic lunar calendar. The start date is the Hijra - when on Friday 16 July 622 CE, Mohammed and his followers
migrated from Mecca to Medina. The calendar consists of 12 alternating months of 30 and 29 days. Although the original calendar determined the start of each month based
on astronomical observation of the first visible crescent after a new moon, a fixed tabular calendar was developed in the 8th century CE. In the tabular calendar,
a day is added to the final (12th) month during leap years making it 30 days long instead of 29. Leap days are added every 2-3 years in a 30 year cycle which is
subject to local variation. The most common distribution is on the 2nd, 5th, 7th, 10th, 13th, 16th, 18th, 21st, 24th, 26th, and 29th year of each 30-year cycle (timeanddate.com).
The Islamic day begins at sundown.
The Coptic Calendar is also known as the Alexandrian Calendar. The Coptic Calendar is coordinated with the Julian Calendar and, since the 4th century CE, used a
starting year (Year 1) from 29 August 284 CE to 28 August 285 CE. A year consists of 13 months where the first 12 months have 30 days each followed an epagomenal
month which has 5 days during normal years and 6 days during leap years. This version of the Coptic calendar is frequently called the Era of Martyrs and is
frequently abbreviated as A.M. (Anno Martyrum). Coptic Leap Years are coordinated with Julian leap years however the coptic leap day is added on the last day
of the coptic year rather than on 29 February. If a Coptic year will encompass a Julian Leap year (i.e. a year where there will be a February 29),
the coptic year will start on 30 August instead of 29 August as 29 August in the previous Coptic year will be a leap day. In years such as this, the
coptic day will be a day ahead of the Julian Calendar until 29 February. Thus, for example while 21 Tuba normally corresponds to 16 January, in a Julian Leap Year
it will correspond to 17 January. The Coptic day begins at sunrise in the civil calendar and sunset in the liturgical version
(Claremont Coptic Encyclopedia).
from Episteme Academy
The Coptic Calendar - Claremont Coptic Encyclopedia
The Coptic Calendar - timeanddate.com
The Coptic Calendar - wikipedia (has a great Coptic Months Table)
The Coptic Calendar by Bishoy Dawood
Converts from Julian to Coptic and other calendars
Chaine, M. (1925). La chronologie des temps chrétiens de l'Égypte et de l'Éthiopie. Paris, P. Geuthner.
The Coptic Calendar (info)
The Coptic Calendar of Martyrs at copticchurch.net
The Hebrew Calendar is also known as the Jewish Calendar or HaLuah HaIvri (הַלּוּחַ הָעִבְרִי) in Hebrew. The Hebrew Calendar is a lunisolar calendar influenced by the Ancient
Babylonian Calendar which has undergone revisions over time. Initially, this calendar was based on sightings of the first crescent after the new moon. After the
destruction of the 2nd temple in 70 CE and throughout the diaspora, the calendar was subject to local variations. By the 4th century CE, a calendar had emerged
which was increasingly based on predicted lunar cycles. Sometime before the 8th century, a fixed 19 year Metonic cycle of intercalations similar to the Babylonian
cycle was adopted and by the early 10th century, the rabbinic calendar had become like the fixed and predictable calendar that is used today. (Stern, 2012:334-335),
The structure of the Hebrew Calendar is one of 12 months with an additional intercalary month added in years 3, 6, 8, 11, 14, 17, and 19 of the
Metonic cycle along with a complicated set of rules (Reingold and Dershowitz, 2018:Section 8.1).
The modern Hebrew Calendar is also characterized by a change in the start date of the calendar from the destruction
of the second Temple in 70 CE to the start of “creation”
like the Anno Mundi Calendar of the Byzantines.
In the Hebrew Calendar, the day begins at sundown.
4.4.1 The Present-Day Rabbinic Calendar: An Outline
from fourmilab. This converter uses modern Hebrew Calendar rules
fourmilab converts from the Hebrew calendar to the Julian Calendar and vice-versa
Episteme Academy web page Converts from the Julian Calendar to Coptic calendar
The Hebrew Calendar - wikipedia
Stern, S. (2001). Calendar and Community: A History of the Jewish Calendar, 2nd Century BCE to 10th Century CE.. .
Seasonal Drift of the Hebrew Calendar
Hebrew Calendar Calculator
The Era of Province Arabia (also called Bostran era, the era of Bostra, the Arabian era, or Provincial era) was a calendar era
(year numbering) with an epoch (start date) corresponding to 22 March 106 AD. It was the official era of
the Roman province of Arabia Petraea, introduced to replace dating by regnal years after the Roman
annexation of the Nabataean Kingdom. It is named after the city of Bostra, which became the
headquarters of the Sixth Legion stationed in the province.
|Enter Year of Province Arabia||Time Span in the Julian Calendar|
The Era of the Olympiads was widely used in ancient texts and is based on the Greek Olympiads which were held every four years. The start date of this calendar is accepted by most modern scholars as 1 July 776 BCE (Finegan, 1998:93). Olympiads (abbreviated Ol.) are four years apart with 4 cycles specifying years within the Olympiad.
|Enter Olympiad Year||Enter Olympiad Cycle (1-4)||Time Span in the Julian Calendar|
Treiger (2015) describes this as follows:
6. The Melkite Era of the Incarnation
The honor of discovering the Melkite era of the Incarnation (AInc), in use from the eleventh to the fourteenth century, belongs to Samir Khalil Samir (Samir 1987). By looking at Melkite colophons where dates “to the divine Incarnation” (li-l-taǧassud al-ilāhī) are given alongside dates according to other eras, he discovered that AInc dates are 8-9 years ahead of AD dates. The conversion key is as follows:
1 January–31 August: AInc–8 = AD;
1 September–31 December: AInc–9 = AD.
Samir, Samir Khalil. “L’ère de l’Incarnation dans les manuscrits arabes melkites du 11e au 14esiècle.” Orientalia Christiana Periodica 53 (1987): 193-201
|Enter Melkite Year||Time Span in the Julian Calendar|
The year of the Incarnation was occassionally used by Theophanes and Anastasius Bibliothecarius (when copying from Theophanes ?). It has a start date of 9 CE (Martin, 1930:12).
|Enter Incarnation Year||Time Span in the Julian Calendar|
Ancient Astronomical Terms
Historical Glossary of Important Terms in Hellenistic Astronomy/a>
Ancient Greek Astronomy and Cosmology
The Precession of the Equinoxes Explained with Graham Hancock - youtube video
Online converters below have not been vetted
Convert a Date - calendarhome.com
Calendar Utility - www.lieberknecht.de