Islamic calendar التقويم الاسلامى

            Islamic calendar

The Islamic calendar or Muslim calendar (Arabic: التقويم الهجري; at-taqwīm al-hijrī; Persian: تقویم هجري قمری ‎ taqwīm-e hejri-ye qamari; also called the Hijri calendar) is the calendar used to date events in many predominantly Muslim countries, and used by Muslims everywhere to determine the proper day on which to celebrate Islamic holy days. It is a lunar calendar having 12 lunar months in a year of about 354 days. Because this lunar year is about 11 days shorter than the solar year, Islamic holy days, although celebrated on fixed dates in their own calendar, usually shift 11 days earlier each successive solar year, such as a year of the Gregorian calendar. Islamic years are also called Hijra years because the first year was the year during which the Hijra occurred— Muhammad‘s emigration from Mecca to Medina. Thus each numbered year is designated either H or AH, the latter being the initials of the Latin anno Hegirae (in the year of the Hijra).^[1]

1.    // Pre-Islamic calendar

The Arabian predecessor to the Islamic calendar was a lunisolar calendar which used lunar months, but was also synchronized with the seasons by the insertion of an additional, intercalary month, when required. Whether the intercalary month (nasi) was added in the spring like that of the Hebrew calendar or in autumn is debated. It is assumed that the intercalary month was added between the twelfth month (the month of the pre-Islamic Hajj) and the first month (Muharram) of this pre-Islamic year^{[citation needed]}. The two Rabi’ months denote grazing and the modern Meccan rainy season (only slightly less arid than normal), which would promote the growth of grasses for grazing, occurs during autumn. These imply a pre-Islamic year beginning near the autumnal equinox. However, the rainy season after which these months are named may have been different when the names originated (before Muhammad’s time) or the calendar may have been imported from another region which did have such a rainy season. On the other hand, the Qur’an forbids the intercalary month (releasing the calendar from the seasons) by Sura 9, verse 36 (believed to have been revealed about the end of Muhammad’s lifetime), which implies a pre-Islamic year beginning near the vernal equinox because that is when the modern lunar year began during his last year.

Months

Islamic Calendar
1.    Muharram 2.    Safar 3.    Rabi’ al-awwal 4.    Rabi’ al-thani 5.    Jumada al-awwal 6.    Jumada al-thani 7.    Rajab 8.    Sha’aban 9.    Ramadan 10.                       Shawwal 11.                       Dhu al-Qi’dah 12.                       Dhu al-Hijjah

The Islamic months are named as follows:^[2]

1.    Muharram محرّم (long form: Muḥarram ul Ḥaram)

2.    Safar صفر (long form: Ṣafar ul Muzaffar)

3.    Rabi’ al-awwal (Rabī’ I) ربيع الأول

4.    Rabi’ al-thani (or Rabī’ al Thānī, or Rabī’ al-Akhir) (Rabī’ II) ربيع الآخر أو ربيع الثاني

5.    Jumada al-awwal (Jumādā I) جمادى الأول

6.    Jumada al-thani (or Jumādā al-akhir) (Jumādā II) جمادى الآخر أو جمادى الثاني

7.    Rajab رجب (long form: Rajab al Murajab)

8.    Sha’aban شعبان (long form: Sha’abān ul Moazam)

9.    Ramadan رمضان (or Ramzān, long form: Ramaḍān ul Mubarak)

10.                       Shawwal شوّال (long form: Shawwal ul Mukarram)

11.                       Dhu al-Qi’dah ذو القعدة

12.                       Dhu al-Hijjah ذو الحجة

Of all the months in the Islamic calendar, Ramaḍān is the most sacred. Between dawn and sunset, Muslims are supposed to abstain from eating, drinking, and sexual intercourse in accordance with the Ramaḍān holiday that lasts throughout the entire month of the same name.

Days of the week

The Islamic week is derived from the Jewish week, as was the medieval Christian week, all of which have numbered weekdays in common. The “first day” of the Islamic week corresponds with Sunday of the planetary week. The Islamic and Jewish weekdays begin at sunset, whereas the medieval Christian and planetary weekdays begin at the following midnight.^[3] Muslims gather for worship at a Masjid at noon on “gathering day”, which corresponds to the sixth day of the Jewish and medieval Christian weeks, and to Friday of the planetary week.

1.    yaum al-ahad يوم الأحد (first day – Sunday) (Urdu, اتوار) (Persian: Yek-Shambeh یکشنبه)

2.    yaum al-ithnayn يوم الإثنين (second day – Monday) (Urdu, پير) (Persian: Do-Shambeh, دوشنبه)

3.    yaum ath-thulaathaa’ يوم الثُّلَاثاء (third day – Tuesday) (Urdu, منگل) (Persian: Seh-Shambeh, سه شنبه)

4.    yaum al-arbia`aa’ يوم الأَرْبِعاء (fourth day – Wednesday) (Urdu, بدھ) (Persian: Chahar-Shambeh, چهارشنبه)

5.    yaum al-khamis يوم الخَمِيس (fifth day – Thursday) (Urdu, جمعرات) (Persian: Panj-Shambeh, پنجشنبه)

6.    yaum al-jumu`a يوم الجُمُعَة (gathering day – Friday) (Urdu, جمعہ) (Persian: Jom’eh, جمعه or Adineh آدينه)

7.    yaum as-sabt يوم السَّبْت (sabbath day – Saturday) (Urdu, ہفتہ) (Persian: Shambeh, شنبه)

Forbidding intercalary months

In the ninth year after the Hijra, as documented in the Qur’an (9:36-37), Allah revealed the prohibition of the intercalary month.

The number of months with Allah has been twelve months by Allah’s ordinance since the day He created the heavens and the earth. Of these four are known as sacred; That is the straight usage, so do not wrong yourselves therein, and fight those who go astray. But know that Allah is with those who restrain themselves.

Verily the transposing (of a prohibited month) is an addition to Unbelief: The Unbelievers are led to wrong thereby: for they make it lawful one year, and forbidden another year, of months forbidden by Allah and make such forbidden ones lawful. The evil of their course seems pleasing to them. But Allah guideth not those who reject Faith.

This prohibition was repeated by Muhammad during his last sermon on Mount Arafat which was delivered during his farewell pilgrimage to Mecca on 9 Dhu al-Hijja 10 AH:

O People, transposing [intercalary months] is an addition to unbelief, through it [God] lead the unbelievers astray: they make it permissible one year and forbid it [at their mere convenience] the next one to elude the timing of what God forbade, so that they make permissible that which Allah forbade [fighting in the forbidden months], and forbid that which Allah has made permissible [fighting in other months]. And [now, this year] time has turned the way it was the day God created Heavens and Earth [The intercalary months since the creation of Heavens and Earth have all canceled out (summed up to whole years)]. The year is twelve months, four of them are forbidden, three successive: Dhu al-Qi’dah and Dhu al-Hijjah and Muharram; and the Rajab of Mudar which is between Jumada and Shaban.^[4]

The three successive forbidden months mentioned by Muhammad (months in which battling is forbidden) are Dhu al-Qi’dah, Dhu al-Hijjah, and Muharram, thus excluding an intercalary month before Muharram. The single forbidden month is Rajab. These months were considered forbidden both within the new Islamic calendar and within the old pagan Meccan calendar, although whether they maintained their “forbidden” status after the conquest of Mecca has been disputed among Islamic scholars.

Numbering the years

According to Islamic tradition, Abraha, governor of Yemen, then a province of the Christian Kingdom of Aksum (Ethiopia), attempted to destroy the Kaaba with an army which included several elephants. Although the raid was unsuccessful, because it was customary to name a year after a major event which occurred during it, that year became known as the Year of the Elephant, which was also the year that Muhammad was born. (See surat al-Fil.) Although most Muslims equate it with the Western year 570, a minority equate it with 571. Later years were numbered from the Year of the Elephant, whether for the years of the pre-Islamic lunisolar calendar, the lunisolar calendar used by Muhammad before he forbade the intercalary month, or the first few years of the lunar calendar thus created. In 638 (AH 17), the second Caliph Umar began numbering the years of the Islamic calendar from the year of the Hijra, which was postdated AH 1. The first day of the first month (1 Muharram) of that proleptic Islamic year, that is, after the removal of all intercalary months between the Hijra and Muhammad’s prohibition of them nine years later, corresponded to July 16, 622 (the actual emigration took place in September).^[1] The first surviving attested use of the Hijri calendar is on a papyrus from Egypt in 22 AH, PERF 558.

Observation of Hilal, date calculations, and nonuniform dates among regions

There is at least one recorded incident in the first Islamic century^[5] where Muslims in Medina and al-Sham fasted independently upon their respective observations of the lunar crescent (Hilal).

Each month has either 29 or 30 days, but usually in no discernible order. Traditionally, the first day of each month was the day (beginning at sunset) of the first sighting of the lunar crescent (the hilāl) shortly after sunset. If the hilāl was not observed immediately after the 29th day of a month, either because clouds blocked its view or because the western sky was still too bright when the moon set, then the day that began at that sunset was the 30th. Such a sighting had to be made by one or more trustworthy men testifying before a committee of Muslim leaders. Determining the most likely day that the hilāl could be observed was a motivation for Muslim interest in astronomy, which put Islam in the forefront of that science for many centuries.

This traditional practice is still followed in a few parts of the world, like India, Pakistan and Jordan. However, in most Muslim countries astronomical rules are followed which allow the calendar to be determined in advance, which is not the case using the traditional method. Malaysia, Indonesia, and a few others begin each month at sunset on the first day that the moon sets after the sun (moonset after sunset). In Egypt, the month begins at sunset on the first day that the moon sets at least five minutes after the sun.

The moon sets progressively later than the sun for locations further west, thus western Muslim countries are more likely to celebrate some holy day one day earlier than eastern Muslim countries.

Umm al-Qura calendar

The official Umm al-Qura calendar of Saudi Arabia used a substantially different astronomical method until recent years [1]. Before AH 1420 (before April 18, 1999), if the moon’s age at sunset in Riyad was at least 12 hours, then the day ending at that sunset was the first day of the month. This often caused the Saudis to celebrate holy days one or even two days before other predominantly Muslim countries, including the dates for the Hajj, which can only be dated using Saudi dates because it is performed in Mecca. During one memorable year during the AH 1380s (the 1970s), different Muslim countries ended the fast of Ramadan on each of four successive days. The celebrations became more uniform beginning in AH 1420. For AH 1420-22, if moonset occurred after sunset at Mecca, then the day beginning at that sunset was the first day of a Saudi month, essentially the same rule used by Malaysia, Indonesia, and others (except for the location from which the hilal was observed). Since the beginning of AH 1423 (March 16, 2002), the rule has been clarified a little by requiring the geocentric conjunction of the sun and moon to occur before sunset, in addition to requiring moonset to occur after sunset at Mecca. This ensures that the moon has moved past the sun by sunset, even though the sky may still be too bright immediately before moonset to actually see the crescent. Strictly speaking, the Umm al-Qura calendar is intended for civil purposes only. Their makers are well aware of the fact that the first visual sighting of the lunar crescent (hilāl) can occur up to two days after the date calculated in the Umm al-Qura calendar. Since AH 1419 (1998/99) several official hilāl sighting committees have been set up by the government of Saudi Arabia to determine the first visual sighting of the lunar crescent at the begin of each lunar month. Nevertheless, the religious authorities of Saudi Arabia also allow the testimony of less experienced observers and thus often announce the sighting of the lunar crescent on a date when none of the official committees could see the lunar crescent.

This is particularly the case for the most important dates on the Islamic calendar — the beginning and end of Ramadan (the month of the fast) and the beginning of Dhu al-Hijja (the month of the annual pilgrimage to Makkah). If a Muslim male resident (two in the case of the end of Ramadan) sees the new moon on the 29th day of the preceding month, and if this sighting is accepted by the religious authorities, then the new month is judged to have arrived, even though the official Umm al-Qura calendar calls for a 30th day before the new month begins. This can change the actual beginning and/or end of the fast (in the case of Ramadan) or the timing of the pilgrimage to Makkah (in the case of Dhu al-Hijja). This happens occasionally, with the most recent occurrences being in AH 1427 (2006-2007), when the beginning of the months of both Ramadan and Dhu al-Hijja occurred a day earlier than called for in the official Umm al-Qura calendar.

Tabular Islamic calendar

Main article: Tabular Islamic calendar

There exists a variation of the Islamic calendar known as the tabular Islamic calendar in which months are worked out by arithmetic rules rather than by observation or astronomical calculation. It has a 30-year cycle with 11 leap years of 355 days and 19 years of 354 days. In the long term, it is accurate to one day in about 2500 years. It also deviates up to about 1 or 2 days in the short term.

Kuwaiti algorithm

Main article: Kuwaiti algorithm

Microsoft uses the “Kuwaiti algorithm” to convert Gregorian dates to the Islamic ones. Microsoft claims that it is based on a statistical analysis of historical data from Kuwait^[6] but it is in fact a variant of the tabular Islamic calendar.^[7]

Important dates

Important dates in the Islamic (Hijri) year are:

• 1 Muharram (Islamic New Year)
• 10 Muharram (Day of Ashurah, Anniversary of the martyrdom of Imam Husayn ibn Ali and his followers.)
• 12 Rabiul Awal (Milad un Nabi for Sunni Muslims)
• 17 Rabiul Awal (Milad un Nabi for Shia Muslims)
• 13 Rajab (Birthday of Imam Ali ibn Abi Talib.)
• 27 Rajab (Isra and Miraj)
• 15 Shabaan (Shab-e-Br’aat, Birthday of Imam Mahdi, the promised Messiah in Islam.)
• 1 Ramadan (first day of fasting)
• 21 Ramadan (Imam Ali ibn Abi Talib‘s death date. He was Mohammad‘s cousin and son in law and the father of Imam Husayn ibn Ali)
• 27 Ramadan (Nuzul Al-Qur’an) (17 Ramadan in Malaysia)
• Last third of Ramadan which includes Laylat al-Qadr
• 1 Shawwal (Eid ul-Fitr)
• 8-10 Dhu al-Hijjah (the Hajj to Makkah)
• 10 Dhu al-Hijjah (Eid ul-Adha).

Current correlations

For a very rough conversion, multiply the Islamic year number by 0.97, and then add 622 to get the Gregorian year number. An Islamic year will be entirely within a Gregorian year of the same number in the year 20,874. The Islamic calendar year of 1429 will occur entirely within the Gregorian calendar year of 2008. Such years occur once every 33 or 34 Islamic years (32 or 33 Gregorian years). More are listed here:

Islamic year within Gregorian year
Islamic	Gregorian	Difference
1228	1813	585
1261	1845	584
1295	1878	583
1329	1911	582
1362	1943	581
1396	1976	580
1429	2008	579
1463	2041	578
1496	2073	577
1530	2106	576
1564	2139	575

Islamic Astronomy Software

The Islamic calendar is based on visibility of the crescent Moon. This is a very difficult scientific problem. We know perfectly well where the Moon and the Sun are at any given time, but how light must the Moon be and how dark must the sky be before we can see the crescent? And what if the weather is bad?

If you want to get a reasonable estimate for when the Moon will be visible, the are several nice pieces of software available.

HM Nautical Almanac Observatory in the UK makes very nice lunar visibility charts. Global First Sighting of New Crescent Moon information is given for the last couple of years. The charts for the current month are also available at Moon Watch.

For many years I have used MoonCalc, developed by Dr. Monzur Ahmed. Unfortunately it is a DOS program, and the lunar visibility charts are done in DOS graphics full screen, so under Windows XP I can no longer capture screenshots. For clear explanations about how to read the MoonCalc charts, please consult How to Read the Visibility Map from Moonsighting.com.

The web page of the Islamic Crescents’ Observation Project (ICOP) has a number of interesting articles. They also host the software Accurate Times by Mohammad Odeh. It is a Windows program for the Islamic calendar, Qiblah direction, and prayer times. There are samples of the lunar visibility charts on Visibility of Ramadan Crescent.

Rules for the Islamic Calendar in Different Countries

In spite of the difficulties, some Muslim communities base their calendar on actual Moon sightings. This is done in India, Pakistan, Bangladesh and the US.

In Saudi Arabia and most of the Gulf countries they have simplified the calendar. They start the lunar month if the Moon sets after the Sun on the 29th day of the previous month, as seen from Mecca. If you don’t believe this, please check out The Actual Saudi Dating System discussion on the web site of the Islamic Crescents’ Observation Project (ICOP).

In Egypt they require moonset to be at least 5 minutes after sunset

The Arithmetical Calendar

Some sources describe an arithmetical (tabular) Islamic calendar. It is sometimes used for approximate conversions for civil purposes, but is not used for religious purposes by Sunnis or Twelver Shi`ites (Ithna Asharia). However, it is common among Sevener Shi`ites (Isma`ili), including the Bohras (Musta’lis) and Nizaris (Isma`ili Khojas, Aga Khanis). It seems to have been designed to be closer to new Moon than to the first visibility of the lunar crescent, so it often runs a day or two ahead of the regular Islamic calendars. There are currently about one million Bohras and about 15 millions Nizaris, compared to over a billion Sunnis and close to a hundred million Twelver Shi`ites. Both of these groups are today primarily Indian Muslim groups, but they trace their history from the Fatimid Caliphate that ruled Egypt from about 970 to 1171. The calendar was put into practice by Imam al-Hakim (985-1021) and is therefore sometimes referred to as the Fatimid or misr (Egyptian) calendar. The calendar is sometimes attributed to the famous astronomer Al-Battani (850-929) and an alternative version to Ulugh Beg (1393-1449). It is also sometimes referred to as hisabi. It is possibly also used by the Qadianis (Ahmadiyyas), but they also seem to use a solar calendar, and they are not considered Muslims by other Muslims.

The average lunar year is about 354 11/30 days, so you get a reasonable lunar calendar by using a cycle of 11 leap years (kasibah) with 355 days in a 30 year cycle. The odd numbered months have 30 days and the even numbered months have 29 days, except in a leap year when the 12th and final month has 30 days. There are several versions for how to space out the 11 leap years. The most common rule is the one followed by the Nizaris Isma`ili, which uses years 2, 5, 7, 10, 13, 16, 18, 21, 24, 26, 29, but some replace 16 by 15 and the Bohras replace 7 by 8, 18 by 19 and 26 by 27. Imran Hussain has both a Bohra and a Sunni version of his Islamic Diary. For more information about the different leap year rules, see Islamic-Western Calendar Converter (Based on the Arithmetical or Tabular Calendar) by Robert H. van Gent.

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            A Brief Introduction To The Islamic (Hijri) Calendar

 

            1. HISTORY AND MOTIVATION

            The Islamic Calendar, which is based purely on lunar cycles, was first introduced in 638 C.E. by the close companion of the Prophet (PBUH) and the second Caliph, `Umar ibn Al-KHaTTab (592-644 C.E.) RAA. He did it in an attempt to rationalize the various, at times conflicting, dating systems used during his time. `Umar consulted with his advisors on the starting date of the new Muslim chronology. It was finally agreed that the most appropriate reference point for the Islamic calendar was the Hijrah. The actual starting date for the Calendar was chosen (on the basis of purely lunar years, counting backwards) to be the first day of the first month (1 MuHarram) of the year of the Hijrah. The Islamic (Hijri) calendar (with dates that fall within the Muslim Era) is usually abbreviated A.H. in Western languages from the latinized Anno Hegirae, “in the year of the Hegira”. MuHarram 1, 1 A.H. corresponds to July 16, 622 C.E.

The Hijrah, which chronicles the migration of the Prophet Muhammad (PBUH) from Makkah to Madinah in September 622 C.E., is the central historical event of early Islam. It led to the foundation of the first Muslim city-state, a turning point in Islamic and world history.

To Muslims, the Hijri calendar is not just a sentimental system of time reckoning and dating important religious events, e.g., Siyaam (fasting) and Hajj (pilgrimage to Makkah). It has a much deeper religious and historical significance.

Muhammad Ilyes [Ilyes84] quotes Nadvi who wrote:

   ``It (the advent of the 15th century) is indeed, a unique occasion to ponder that the Islamic Era did not start with the victories of Islamic wars, nor with the birth or death of the prophet (PBUH), nor with the Revelation itself.  It starts with Hijra, or the sacrifice for the cause of Truth and for the preservation of the Revelation.

     It was a divinely inspired selection.  God wanted to teach man that struggle between Truth and Evil is eternal.  The Islamic year reminds Muslims every year not of the pomp and glory of Islam but of its sacrifice and prepares them to do the same.''

             

            From a historical angle, Ilyes quotes Samiullah who writes:

    ``All the events of Islamic history, especially those which took place during the life of the Holy Prophet and afterwards are quoted in the Hijra calendar era.  But our calculations in the Gregorian calendar keep us away from those events and happenings, which are pregnant of admonitory lessons and guiding instructions. 

      ...And this chronological study is possible only by adopting the Hijri calendar to indicate the year and the lunar month in line with our cherished traditions.''

             

            2. SPECIFICATION AND METHOD

The Islamic (Hijri) year consists of twelve (purely lunar) months. They are: (1) MuHarram; (2) Safar; (3) Raby` al-awal; (4) Raby` al-THaany; (5) Jumaada al-awal; (6) Jumaada al-THaany; (7) Rajab; (8) SHa`baan; (9) RamaDHaan; (10) SHawwal; (11) Thw al-Qi`dah; and (12) Thw al-Hijjah.

The most important dates in the Islamic (Hijri) year are: 1 MuHarram (Islamic new year); 27 Rajab (Isra & Miraj); 1 RamaDHaan (first day of fasting); 17 RamaDHan (Nuzul Al-Qur’an); Last 10 days of RamaDHaan which include Laylatu al-Qadar; 1 SHawwal (`iyd al-fiTr); 8-10 Thw al-Hijjah (the Hajj to Makkah); and 10 Thw al-Hijjah (`iyd al-’aDHHaa’).

It is considered a divine command to use a (Hijra) calendar with 12 (purely) lunar months without intercalation [Ilyes84], as evident from the following verses of the Holy Qur’an (Trans: A. Yusuf Ali):

     They ask thee the New Moons Say: They are but signs To mark fixed periods of time In (the affairs of) men And for Pilgrimage.   (II:189)

     The number of months In the sight of Allah Is twelve (in a year) So ordained by Him The day He created The heavens and the earth; Of them four are sacred; That is the straight usage So wrong not yourselves Therein, and fight the Pagans. (IX: 36)

     Verily the transposing (Of a prohibited month) Is an addition to Unbelief: The Unbelievers are led To wrong thereby: for they make it lawful one year, And forbidden another year, Of months forbidden by Allah And make such forbidden ones Lawful.  The evil of their course Seems pleasing to them. But Allah guideth not Those who reject Faith.  (IX: 37)

            Since the Islamic calendar is purely lunar, as opposed to solar or luni-solar, the Muslim (Hijri) year is shorter than the Gregorian year by about 11 days, and months in the Islamic (Hijri) year are not related to seasons, which are fundamentally determined by the solar cycle. This means that important Muslim festivals, which always fall in the same Hijri month, may occur in different seasons. For example, the Hajj and RamDHaan can take place in the summer as well as the winter. It is only over a 33 year cycle that lunar months take a complete turn and fall during the same season.

For religious reasons, the beginning of a Hijri month is marked not by the start of a new moon, but by a physical (i.e., an actual human) sighting of the crescent moon at a given locale. From the Fiqhi standpoint, one may begin the fast in RamDHaan, for example, based on “local” sighting (IKHTILAF AL-MATALE’) or based on sighting anywhere in the Muslim World (ITTEHAD AL-MATALE’). Although different, both of these positions are valid Fiqhi positions.

Astronomically, some data are definitive and conclusive (i.e. the time of the BIRTH of a new moon). However, determining the VISIBILITY of the crescent is not as definitive or conclusive; rather it is dependent upon several factors, mostly optical in nature. This makes it difficult to produce (in advance) Islamic calendars that are reliable (in the sense that they are consistent with actual crescent visibility).

Efforts for obtaining an astronomical criterion for predicting the time of first lunar visibility go back the the Babylonian era, with significant improvements and work done later by Muslim and other scientists. These efforts have resulted in the development in a number of criteria for predicting first possible sighting of a crescent. However, there remains a measure of uncertainty associated with all criteria developed thus far. Moreover, there has been little work in the area of estimating crescent visibility on global (as opposed to local) scale. Until this happens, no Hijri calendar software can be 100% reliable, and actual crescent sighting remains essential especially for fixing important dates such as the beginning of Ramadan and the two `iyds.

The slight differences in printed Islamic calendars, worldwide, can therefore be traced to two primary factors: (1) the absence of a global criterion for first visibility; and (2) the use of different visibility criterion (or method of calculation). Weather conditions and differences in the observer’s location also explain why there are sometimes differences in the observances of Islamic dates, worldwide.

Readers interested in further information should consult Mohammad Ilyas’ excellent book “A Modern Guide to Astronomical Calculations of Islamic Calendar, Times & Qibla,” Berita Publishing, 1984, (ISBN: 967-969-009-1). The book contains a thorough discussion of the Islamic calendrical system and related historical and scientific developments. It also presents an interesting proposal for a universal Islamic Calendar based on a global visibility criterion and the concept of a Lunar Day (or International Lunar Date Line).