CHRONOS

from romannumerals.co

from romannumerals.co

Julian Day Calculations allow you to figure out the day of the week.

Hour (0-24)	Day	Month	Year	Local Longitude	Specify E or W Longitude 1 - East 2 - West	Standard Julian Day (12 hour UT)	Local Julian Day	Weekday

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Hover over underlined variables for pop up explanations. The calculator above computes Julian Day and day of the week for the Julian and Gregorian calendars and is valid from noon 1 January 4713 BCE until present. In these calendars, a new day begins at midnight. Lunar and lunisolar local calendars (e.g., Islamic, Hebrew, Syriac, and Coptic Liturgical Calendars) start their day at night fall and solar calendars (e.g., Coptic Civil Calendar) start their day at sunrise. Make adjustments to the day of the week accordingly (see illustration below).

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 Gregorian Calendar went into effect in October 1582 CE. It was adopted by various countries and entities after this date - replacing the earlier Julian Calendar. One notable holdout is the Greek Orthodox Church which still uses the Julain Calendar.

from fourmilab

Meeus, J. (1991). Astronomical algorithms. Richmond, Virginia USA, Willmann-Bell Inc., pages 60-65

Gregorian calendar - wikipedia

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).

Calendaric Inconsistencies of Individual Authors

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

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The Byzantine Calendar - wikipedia

Byzantine Creation Era Calendar

Anno Mundi Calendar Google Sheet (not fully QCed)

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 (Bickerman, 1980:78).

Input	Start Year (CE)	Notes
Starting Year		Invalid before 312 CE
Indiction	Year (CE)	Indiction Time Span outside of Egypt

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Indictions - wikipedia

Chart of Indictions

Indictions Google Sheet

Regnal Year	Start Day	Start Month	Start Year (CE)	Time Span in the Julian Calendar

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Regnal Years Google Sheets (not fully QCed)

The Anno Graecorum (A.G.) Calendar is also known as the Seleucid Era, Chaldean, or the Macedonian Calendar. 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 Months and Julian equivalent dates
Sources: Meimaris and Kritikakou (2005) and Theodossiou et al (1997)

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

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Syriac Calendar

Names of months and days in the Syriac Calendar

Automating the Liturgical Calendar of the Syriac Orthodox Church

A.G. Calendar Google Sheets (not fully QCed)

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.

from fourmilab

fourmilab converts from the Islamic calendar to the Julian Calendar and vice-versa

The Islamic Calendar - timeanddate.com

Islamic Calendar Google Sheet (not fully QCed)

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.

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. The Bostran era 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

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Bostran Era - wikipedia

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

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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.

Bibliography

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

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The year of the Incarnation was occasionally used by Syncellos/Theophanes and Anastasius Bibliothecarius (when copying from Theophanes ?). It has a start date of 9 CE (Martin, 1930:12). This calculator is based on the assumption that year 1 of the divine incarnation year was from 25 March 9 to 24 March 10 CE which equates to A.M._a 5501 (Adler and Tuffin, 2002:lxxi-lxxiv). This is what Syncellos used. Absent further investigation, I cannot guarantee that Theophanes and Anastasius Bibliothecarius rigorously applied this calculation methodology.

Enter Incarnation Year	Time Span in the Julian Calendar

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Adler, W., et al. (2002). The Chronography of George Synkellos: A Byzantine Chronicle of Universal History from the Creation, Oxford University Press.

Martin, E. J. (1930:12). A history of the iconoclastic controversy. London, Society for Promoting Christian Knowledge.

Finegan (1998) describes the Year of Abraham as follows

With regard to the years of Abraham in Helm's edition of the Chronicle of Eusebius: like the Olympiadic dates (§308), the Abrahamic dates are stated in single-year figures but are to be understood as overlapping two years. Thus the generally accepted date of the first year of Abraham, which is marked as equivalent to 2016 B.C.,⁹⁸ is to be understood as 2016/2015 B.C.; and the further years of Abraham in our Table 75 are all to be understood in the same way." The correctness of the initial dates of 776/775 B.C. for the sequence of Olympiadic years (§308 Table 46) and of 2016/2015 B.C. for the sequence of years of Abraham (§309 Table 75) in the Chronicle of Eusebius (Jerome) will be confirmed at the place where the Chronicle comes to a well-known point in Babylonian and biblical chronology, namely, the second year of the Persian king, Darius I (§§330-333, Tables 89, 90). Theoretically an overlap could be either forward or backward; e.g., the year A.D. 68 could mean either 68/69 or 67/68 (cf. §671).

For extrapolating years not shown in this table, note that (a) the sum of any year B.C. and the corresponding A.Abr. year is 2017; and (b) any A.D. year is always 2016 less than the corresponding A.Abr. year.

Footnotes

98 Helm20a-20b.

Enter Year of Abraham	Time Span in the Julian Calendar

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Finegan, J. (1998). Handbook of biblical chronology : principles of time reckoning in the ancient world and problems of chronology in the Bible. Peabody, Mass., Hendrickson Publishers.

Malalas defined the start of Era of Antioch in Book 9 [217] of his Chronicle.

Gaius Julius Caesar entered Antioch on the 23rd day of the month of Artemisius; he constructed a basilica, which he called the Caesarium, opposite the temple of Ares that was afterwards called the Macellum, and there he erected a bronze statue to the Fortune of Rome. He also constructed, on the so-called acropolis in the upper part of Antioch the great, public baths for the use of the inhabitants of the acropolis; he brought the water for the baths [217] from the spring of the Laodicean Way, along an aqueduct that he constructed. And there in the upper part [of the city] he constructed an arena for gladiators and a theatre; he also restored the Pantheon, which was about to collapse, and erected an altar.

Then this Caesar went off to Alexandria the great and constructed there, naming it after his son by his beautiful concubine Cleopatra - he found this Cleopatra in the Thebaid, where she had been banished by her brother Ptolemy, who was hostile towards her; Caesar seduced [Cleopatra] and made her pregnant; and she bore a son, whom she called Caesarion - so Julius Caesar constructed the Caesarium in Alexandria the great, naming it after his own son. He expelled Cleopatra's brother Ptolemy from the kingdom of Egypt, and gave the kingdom of Egypt to Cleopatra, after killing the two eunuchs who had persuaded Ptolemy to banish her to the Thebaid. But the son of Cleopatra and Caesar died while he was still young.

When Caesar returned to Rome, he was murdered by the second Brutus and the other senators who conspired with him, in the consulship of (?) Isauricus and Antonius (for the second time). Therefore the first year of the era of Antioch the great is counted from this year, in honour of Gaius Julius Caesar.

Downey (1963:283) dates Julius Caesar's visit to Antioch to 47 BCE. Julius Caesar was assassinated on 15 March 44 BCE.

In discussing the Trajan Quake, Ambraseys (2009:123) equates the Antiochene Year of 164 with October 115 - September 116 CE where a typo appears to have reduced his reference to the number 116. In discussing an Earthquake in 458 CE in Antioch, Ambraseys (2009:169) equates the Antiochene Year of 506 with 1 October 457 to 30 September 458. For now, this calculator is based on these calibration points which seem to date Julius Caesar's visit to Antioch to between 1 Oct. 49 BCE and 30 Sept. 48 BCE, differing with Downey (1963:283).

Parise (2002) defines the Era of Antioch a year later than Ambraseys (2009:123, 169) and also has different start and end dates. A summary for few different years is provided below:

Era of Antioch Greek	New Years Day (Julian)	Era of Antioch Syrian	New Years Day (Julian)
1	4 Sept. 48 BCE	1	9 Aug 48 BCE
32	5 Sept. 17 BCE	32	8 Aug 48 BCE
		48	8 Aug 1 BCE
		49	9 Aug 1 CE
332	5 Sept. 284 CE	332	8 Aug 284 BCE

Since Ambraseys (2009:123), Guidoboni et al (1994), and Downey (1963:283) date the Trajan Quake to 13 December 115 CE apparently based on Malalas' specification of the Antiochene Year of 164, I am going to assume for now that they were correct although it is possible that Ambraseys (2009:123) and Guidoboni et al (1994) relied on Downey (1963:283) and Downey (1963:283) made a mistake.

Downey (1961) dates the founding of Antioch by the Seleucids to May 300 BCE and the founding of Seleucia Piera to April 300 BCE.

Enter Antiochene Year	Time Span in the Julian Calendar

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Ambraseys, N. (2009). Earthquakes in the Mediterranean and Middle East: a multidisciplinary study of seismicity up to 1900. Cambridge, UK, Cambridge University Press.

Glanville Downey, A. (1961). History of Antioch in Syria from Seleucus to the Arab Conquest, Princeton Univ. Press, New Jersey, Princeton.

Downey, G. (1963). Ancient Antioch, Princeton University Press.

Parise, F. (2002). The Book of Calendars: Conversion Tables for Ancient, African, Near Eastern, Indian, Asian, Central American and Western Calendars Gorgias Press.

The wikipedia entry for the Armenian Calendar provides the following:

• The Armenian calendar is based on an invariant year length of 365 days
• Year 1 of the Armenian calendar began on 11 July 552 of the Julian calendar
• The Armenian calendar is divided into 12 months of 30 days each, plus an additional (epagomenal) five days, called aweleacʿ ("superfluous")
• Years are usually given in Armenian numerals; which are letters of the Armenian alphabet preceded by the abbreviation ԹՎ for t’vin, meaning "in the year." For example, ԹՎ ՌՆԾԵ, which means "the year 1455."

Tables below come from the wikipedia entry for the Armenian Calendar.

Months of the year

#	Armenian	H-M Romaniz.	Meaning	Etymology/Notes
1	նաւասարդ	nawasard	new year	Avestan*nava sarəδa
2	հոռի	hoṙi	two	From Georgian ორი (ori) meaning "two"
3	սահմի	sahmi	three	From Georgian სამი (sami) meaning "three"
4	տրէ	trē		Zoroastrian Tïr
5	քաղոց	kʿałocʿ	month of crops	From Old Armenian քաղեմ (kʿałem) meaning "to gather" from PIE *kʷl̥-
6	արաց	aracʿ	harvest-time	From old armenian արաց[4](aracʿ), meaning harvest time, harvest of grape/fruit
7	մեհեկան	mehekan	festival of Mithra	Iranian *mihrakān-; Zoroastrian Mitrō
8	արեգ	areg	sun month	From Old Armenian արեւ (arew) meaning "sun" from PIE *h₂rew-i- also meaning sun
9	ահեկան	ahekan	fire festival	Iranian *āhrakān-; Zoroastrian Ātarō
10	մարերի	mareri	mid-year	Avestan maiδyaīrya; Zoroastrian Dīn
11	մարգաց	margacʿ
12	հրոտից	hroticʿ		Pahlavi *fravartakān; Zoroastrian Spendarmat̰
13	աւելեաց[5]	aweleacʿ	redundant, superfluous	Epagomenal days

Days of the month

#	Name	Armenian Text	Meaning/derivation
1	Areg	Արէկ	sun
2	Hrand	Հրանդ	earth mixed with fire
3	Aram	Արամ
4	Margar	Մարգար	prophet
5	Ahrank’	Ահրանկ	half-burned
6	Mazdeł
7	Astłik	Աստղիկ	Astłik
8	Mihr	Միհր	Mihr (Armenian deity)
9	Jopaber		tumultuous
10	Murç	Մուրց	triumph
11	Erezhan		hermit
12	Ani	Անի	name of a city
13	Parkhar
14	Vanat	Վանատ	host, refectioner of a monastery
15	Aramazd	Արամազդ	Aramazd
16	Mani	Մանի	beginning
17	Asak	Ասակ	beginningless
18	Masis	Մասիս	Mount Ararat
19	Anahit	Անահիտ	Anahit (Armenian goddess)
20	Aragats	Արագած	Mount Aragats
21	Gorgor		Name of a mountain
22	Kordvik		6th province in Armenia Major
23	Tsmak	Ծմակ	east wind
24	Lusnak	Լուսնակ	half-moon
25	Tsrōn		dispersion
26	Npat	Նպատ	Apam Napat
27	Vahagn	Վահագն	Zoroastrian Vahrām; Avestan Verethragna, name of the 20th day
28	Sim	Սիմ	mountain
29	Varag	Վարագ	name of a mountain
30	Gišeravar		evening star

from Clear Sky Tonight - appears to use Julian Calendar prior to 1582 CE

from Clear Sky Tonight - appears to use Julian Calendar prior to 1582 CE

from Clear Sky Tonight - appears to use Julian Calendar prior to 1582 CE

• from imcee
• Note that imcee outputs all dates in the Gregorian Calendar even during the time period when the Julian Calendar was in use.
• Other Calculators at imcee

• from imcee
• Note that imcee outputs all dates in the Gregorian Calendar even during the time period when the Julian Calendar was in use.
• Other Calculators at imcee

Ancient Astronomical Terms

Historical Glossary of Important Terms in Hellenistic Astronomy

Ancient Greek Astronomy and Cosmology

The Precession of the Equinoxes Explained with Graham Hancock - youtube video

Online converters below have not been vetted

Calendarical software

Convert a Date - calendarhome.com

Calendar Utility - www.lieberknecht.de