The determination for the beginning of the month related to the Hijri calendar was initially applied locally with a limited coverage area. However, in the current globalisation era, different decisions for the beginning of the month in various countries often confuse. Therefore, the discourse on the Hijri calendar unification has emerged to prevent the differences regarding Eid al-Fitr and Eid al-Adha. According to Djamaluddin (2011a), there are three prerequisites for realising an established calendar, namely (1) boundaries on the enforceability area, (2) single authority and (3) agreed criteria. These three prerequisites should be agreed upon to obtain an established calendar.

Fiqh related to the ‘matlak’ issue can expand the enforceability area. The concept of matlak was originally related to the enforceability of the testimony of rukyat hilal, which is an observation of the first crescent. However, it is also extended to the concept of calendar enforceability. Matlak is still a matter of debate, specifically when discussing global calendar unification. It is related to the enforceability of the rukyat and is limited to tracing this study from various sources, with no consensus (ijma’) and general perspective.

Ulemas in addressing the issue of matlak are divided into several perspectives (Muhammad Hani Sa’i 2007). Firstly, each country refers to the results of its rukyat, and secondly, neighbouring nations should also fast when the hilal is sighted. Thirdly, when rukyat succeeds, all countries, far and near, are obliged to follow.

Meanwhile, regarding the enforceability area of rukyat, according to Abdurrahman al-Jaziri in al-Fiqh’ ala Mazahib al-Arba’ah (al-Jaziri 1999), three of the four well-known fiqh ulemas (Hanafi, Maliki, Hambali) (as-Sabuni 1999) tend to support global rukyat where a people’s testimony applies to Muslims around the world. In contrast, the Shafi’iyah school of thought prefers local rukyat, which only applies to one matlak of around a 24 farsakh radius (about 120 km).

Wahbah az-Zuhaili, in the work of al-Fiqh al-Islami wa Adillatuhu (az-Zuhaili 1985), stated that the Shafi’iyah circle determines the radius related to the matlak between far and near areas. However, an-Nawawi in al-Majmu’ Syarh al-Muhazzab reported that there are three perspectives related to the criteria of far and near areas according to Syafi’iyah. The first perspective is that it is considered as far for the area in different matlak and as near for area in the same matlak. This is the most valid opinion among them. The second is that the benchmark is territorial unity, indicating it is considered a near area when it is in the same area. The third perspective is that it is seen as a far area when it reaches the qasar distance (89 km) and as a near area when less than the qasar distance (an-Nawawi n.d.).

Based on the fiqh perspective, the enforceability area of the Hijri calendar can be global. However, local rukyat is still valid in many countries, which is also related to the perspective of rukyat proof [hilal observation]. The concept of wilayah al-hukmi initiated by Syafi’iyah can also bridge global calendar enforcement when one jurisdiction can be accepted. The idea of one jurisdiction will be discussed further in socio-political studies.

Astronomical studies contribute to the proposed hilal visibility criteria based on long-term rukyat data from various regions globally. Astronomical parameters related to the hilal visibility need to be studied in terms of the types and the value used as the minimum limit for the sighting. The parameter that describes the hilal physique and disturbances on the horizon are usually used (Qureshi 2005; Ahmed 2020:10; Ridpath 2012; Zainon et al. 2019, Djamaluddin 2011b)

Astronomy considers rukyat and hisab to be equivalent and can replace each other. Hisab is built with a formulation based on long-term rukyat data. Meanwhile, a very thin rukyat hilal is assisted with hisab results to make it easier to direct the sight and clarify the doubtful results. Astronomy can bridge rukyat and hisab without contradicting the arguments. Rukyat practitioners still believe in their arguments, while hisab can also stick with the beliefs of their arguments (Djamaluddin 2013).

The problem of determining the beginning of the Hijri month involves various aspects that are complexly interrelated, such as fiqh, scientific and socio-political. Astronomy plays a role as a tool in determining the beginning of the month from a scientific point of view. With the involvement of astronomy, the differences between Muslims in determining holidays and the preparation of the calendar can be unified (Setyanto 2008).

The position of science regarding the hilal is for operational purposes in implementing the Shari’a regarding the determination of the beginning of the Islamic month. The essence of rukyat hilal [observation] can be taken as a reference in hisab [calculation] to predict the hilal visibility. According to scientific studies, hisab and rukyat are a unit that synergises with one another. Hisab, or a model for calculating the precise positions of the moon and sun by including corrections, is impossible to be built without precise data from rukyat. Furthermore, hisab, for determining the beginning of the Islamic month, not only calculates the position of the moon and the sun but also uses the correct and careful criteria for the hilal visibility. Rukyat hilal is also used to test the hisab prediction results about hilal visibility. Repeated testing and theoretical understanding regarding the formation can create science about the hilal (Raharto 2009).

The hilal, understood from an astronomical perspective as a crescent of a certain size can have many definitions. In contrast, it is only one and can be recognised by the naked eye. The physique is part of the moon’s phases, which is the only natural satellite of Earth (Raharto 2009). The visibility criteria is an astronomical study that continues to grow, not just to determine the beginning of the lunar month for Muslims. The physical condition of the hilal due to the illumination (lighting) on the moon and the scattering of sunlight by the atmosphere on the horizon are two important aspects of hilal of crescent visibility (Allawi 2022:186; Djamaluddin 2011a).

In general, to predict the hilal visibility, the following parameters are often used (Ahmad et al. 2020; Alhammadi et al. 2019; Alrefay et al. 2018; Fatoohi, Stephenson & Al-Dargazelli 1999; Ilyas 1994:425; N. Nugali pers. comm., 2023):

Muslims, as a religious group, have their own cultural identity. They are promoted to maintain and uphold their identity as part of Islamic civilisation and a manifestation of the faith. The identity of Muslims, called Islamic culture or civilisation, is based on Allah’s revelation and the sunnah of the Prophet, including tradition, art, morality, customs, Arabic language, and knowledge system that contains the lunar (Hijri) calendar system (Butar-Butar 2014).

The history of Islamic civilisation is knowledge regarding all aspects of the progress of Muslims in history, which is oriented towards major religious events from the time of the Prophet Muhammad to the Caliph Umar bin Khattab known as the classical period. Islamic civilisation history is interpreted as the development or progress of the culture, which includes three different meanings. The first is the progress and level of intellectual intelligence produced in a period of Islamic rule, starting from the time of Prophet Muhammad until the development of Islam currently. The second is the results achieved in the fields of literature, science, and art. The third is political progress or Islamic power, specifically related to worship, use of language and social habits (Abdurrahman 2011).

The areas of experts and common people become the impact of the establishment of the Hijri calendar. The experts have a task in determining the Hijri calendar system, and the people who are unfamiliar with the knowledge can carry out their worship according to the correct time setting and the Shari’a (Satria Hamdani & Alhamuddin 2015).

From a sociological perspective, several types of approach theory can be applied to the Hijri calendar system, such as the structural-functional, the conflict, and the symbolic-interactionalism approach. The structural-functional approach is based on two basic assumptions. Firstly, society consists of substructures whose functions are interdependent. Therefore, changes in substructure can automatically be reflected in other structures. Secondly, each structure supports other activities or substructures in a social system (Farid Ahmad 1996).

The last theory is the symbolic-interactionism approach as a micro-perspective in sociology based on social interaction at the minimum level. This micro level is expected to broaden the scope of its analysis to capture the whole community as a determinant for the processes of many interactions. The community, unfamiliar with the science of hisab and rukyat, belongs to the micro-group category that cannot participate in determining the Hijri calendar. However, these experts expect this kind of support from the community to improve further groups who want to advance their schools. The community wants unity during worship time among Muslims in Indonesia. It is expected that harmony will be created in worship, fasting, Eid al-Fitr, and Eid al-Adha (Satria Hamdani & Alhamuddin 2015).

Problems with the International Islamic Calendar are felt in various countries inhabited by the Muslim community. This problem can be seen from several methods used in determining the beginning of the Hijri month. The differences are often described as disputes over the use of methods, namely hisab and rukyat. The unified Islamic calendar continues to grow, as evidenced by the creation of several Muslim scholars focused on this problem, with different methods and criteria. This is the initial hope for creating an established calendar that can be used internationally (Yaqin 2020).

According to Spencer’s theory, as quoted by Basthoni (2018), the evolution process of the Islamic calendar system entered the integration process. Attempts to unify the Islamic calendar began to bloom. In historical records, this effort continues to be carried out by astronomers and the government authority. The efforts revolve around determining mutually accepted criteria, enforceability limits, and date lines. Meanwhile, the global concern of Muslims regarding the sociological impact is that scientific products cannot be implemented in formulating the determination of the international Islamic calendar. This is an intellectual challenge to avoid differences in determining the implementation of worship times. The intellectual notion as an alternative solution is a process of metamorphosis closely related to social upheaval and political conditions, cultural acculturation, economic turmoil, and religious understanding. A unified Islamic calendar is needed to answer the global concerns of Muslims to avoid division or hostility.

Socio-political studies are needed relating to the elements of authority that determine the implementation of the Hijri calendar. In fiqh studies, wilayah al-hukmi can be a bridge to reach common ground, and in this concept, there are judges or authorities in a jurisdiction. The authority resolves the differences and defines the boundaries for the enforceability area of the calendar as well as the selection of criteria to be applied. It includes the Government of Indonesia or several others, such as MABIMS, as the collective government of Brunei Darussalam, Indonesia, Malaysia, and Singapore.

According to Hasbi, as quoted by Azhari (2015), since Mu’awiyah and Ibn Abbas became caliph and governor in Damascus and Medina, there has been a difference of opinion in dealing with holidays. The lack of good relations between the central and regional governments triggers this difference. However, according to Syamsul Anwar in Azhari (2015), the difference between Mu’awiyah and Ibn Abbas, based on astronomical and historical analysis, is estimated to have appeared in 35 H or 655 AD before the killing of the Caliph Usman bin Affan. The difference in perspective occurs because Hasbi emphasised the hadith matan aspect, which sees an inharmonious relationship between the central and regional governments in starting and ending the Ramadhan fast. Meanwhile, Syamsul Anwar looked at the sanad aspect with an emphasis on Ramadhan’s events, where rukyat can occur on Friday nights.

In the Indonesian context, efforts to unify the determination for the beginning of the lunar month have been conducted since the establishment of the Hisab Rukyat Board, Ministry of Religious Affairs in 1976 and are still being pursued. These unification efforts are in the form of deliberations, consultations, studies, training, joint observations, joint hisab work meetings, as well as preparation and dissemination of a relatively easy contemporary hisab system (Widiana 2005).

In the Indonesian context, at the national level, unification efforts occurred at the Cisarua meeting in Bogor in 2011. This meeting resulted in an agreement to modify the criteria for imkan rukyat as well as affirm its function as a temporary criterion before more acceptable criteria are realised (Sudibyo 2016). The new criteria drafts for the hilal visibility or imkan rukyat were also discussed at a national level meeting in Jakarta on 14–15 August 2015 M or 29–30 Shawwal 1436 H entitled ‘Unification of Methods for Determining the Beginning of Ramadhan, Shawwal, and Dzulhijjah’ by the Indonesian Ministry of Religious Affairs (Government) with the Indonesian Ulema Council (MUI) with Islamic organisations in Indonesia. This activity was followed up with a meeting of astronomers on 21 August 2015, M/6 Dzulqa’dah 1436 H in Jakarta. The main agenda was to discuss determining the criteria for the beginning of the Hijri month, and the results were submitted to MUI before the 2015 National Conference. The proposed ‘MUI Criteria’ drafts, namely the hilal height of 3 and the elongation of 6.4 degrees, are used to determine the beginning of the Hijri month (Djamaluddin 2016a).

The proposed new criteria in the form of a minimum moon height of 3 degrees refer to global data from Ilyas (1994) and Caldwell and Laney (2001). Based on these global data, there is no reliable rukyat hilal data when the difference between the moon and sun height is less than 4 degrees or the moon height is less than 3 degrees. Minimum elongation of 6.4 degrees is obtained from Odeh’s compilation of global observational data (2006). The criteria for the moon height describe the disturbance factor of the twilight on the western horizon, where the higher the moon, the weaker the disturbance factor. Meanwhile, the elongation parameter describes the physical factors of the hilal, where the greater the elongation, the thicker the hilal.

At the Southeast Asian level, unification efforts have been conducted through the MABIMS conference. The last conference took place in Indonesia in 2014 and made several recommendations. For example, MABIMS countries need to jointly apply the criteria in determining the beginning of the lunar month by always carrying out coordination. Furthermore, a study is needed in the presence of relevant ulemas, astronomers and scholars to discuss and determine the new MABIMS criteria (Djamaluddin 2016a).

At a regional level meeting in Malaysia, the Conference of the MABIMS on 02–04 August 2016 M or 27 Shawwal to 1 Dzulqa’dah 1437 H produced proposed ‘Ministers of Religious Affairs of Brunei Darussalam, Indonesia, Malaysia and Singapore new criteria’ drafts, namely the hilal height of 3 and the elongation of 6.4 degrees, which the elongation is the angular distance from the centre of the moon to the sun (Djamaluddin 2016b). These are a correction to the criteria for imkan rukyat MABIMS from a hilal height of 2 degrees with a moon-sun distance of 3 or an age of 8 h (Kementerian Agama Republik Indonesia 1998).

After the new MABIMS hilal visibility criteria were ratified on 08 December 2021 at the regional level by the Ministers of Religious Affairs of four Southeast Asian countries, the need to accept the criteria in determining the beginning of the Hijri month became important. According to Thomas Djamaluddin, there are at least six underlying reasons. Firstly, the MABIMS criteria are built based on long-term global observations. Secondly, the parameters are commonly used by Indonesian hisab experts, namely the hilal height and elongation. Thirdly, the physical aspects of the rukyatul hilal are described. Elongation analyses the physical thickness of the hilal, where the greater the value, the thicker the hilal. Fourthly, in the MABIMS criteria, a minimum height of 3 degrees is based on global data. Therefore, the hilal below 3 degrees cannot be seen because of the disturbance from the strong twilight. Fifthly, a minimum elongation of 6.4 degrees is based on the record for the closest moon, as reported by Mohammad Shawkat Odeh, one of the international astronomers. An elongation of fewer than 6.4 degrees is too thin and dim to beat the twilight. Sixthly, the new criteria built are common ground for users of the rukyat and hisab methods, such as Nahdlatul Ulama (NU) and Muhammadiyah, respectively (republika.co.id 2022).

The response of NU in applying the new criteria for imkan rukyat should also be discussed. This is because the nu.or.id website stated that Nahdliyin astronomical scholars can accept the new MABIMS criteria as NU’s imkan rukyah criteria. However, NU is a jam’iyyah with its own rules and the acceptance of the criteria can formally cross its path. In other words, one of the determining factors is the determination of the Astronomical Institute for the Nahdlatul Ulama Executive Board (PBNU), with the administrators of other institutions in PBNU (Sudibyo 2022).

According to the Head of the Astronomical Observatory at the Muhammadiyah University of North Sumatra (OIF UMSU), Arwin Juli Butar-Butar stated that these new criteria in the future are predicted to face implementation challenges in the field. The difficulties and issues with MABIMS criterion 3–6.4 are attributable to the absence of a clear topocentric-geocentric formula for the moon’s height and elongation, where variations in their application result in different parameter numbers (Ilham 2022).

The challenge of implementing the Neo MABIMS criteria is inseparable from the nature of the established calendar, which requires the agreement of the following: (1) boundaries of the enforceability area (national or global), (2) single authority and (3) criteria (Djamaluddin 2011a).

Ministers of Religious Affairs of Brunei Darussalam, Indonesia, Malaysia and Singapore is an intergovernmental organisation comprising of four Southeast Asian countries, namely Brunei Darussalam, Indonesia, Malaysia and Singapore. In 2021, MABIMS adopted a new criteria aimed at unifying the Islamic calendar of member countries to promote regional integration (Djamaluddin 2022). The agreement aims to establish a common calendar that will harmonise the holidays, festivals, and other important dates across the region.

The new MABIMS policy has the potential to create conflicts in society, particularly among communities that are deeply attached to their traditional calendars. The dynamics of managing such conflicts will depend on several factors, including the nature and extent of the conflicts, the level of involvement of the government of member states, and the strategies used to promote the policy.

One potential source of conflict is the religious and cultural diversity of the region. The proposed calendar would need to take into account the diverse religious and cultural traditions of the member states to be acceptable to all. Thus, the MABIMS policy will need to strike a balance between promoting regional integration and respecting the cultural and religious diversity of the member countries, as well as the Islamic organisations.

Another potential source of conflict is the varying degrees of readiness and willingness among member states to implement the policy. Some countries may be more enthusiastic about the policy than others, which could lead to resistance or reluctance to participate fully. Thus, the MABIMS policy will need to address these disparities to ensure that the unification of calendars is implemented effectively and smoothly.

To manage conflicts that arise in society about unifying calendars, MABIMS may employ a variety of strategies. For instance, it may engage in extensive consultations with stakeholders, including religious and cultural leaders, to build consensus on the proposed calendar. MABIMS may also conduct public awareness campaigns to educate the public about the benefits of the policy and address any concerns or misconceptions that may arise.

In conclusion, the new MABIMS policy aimed at unifying calendars has the potential to create conflicts in society. However, with the appropriate strategies in place, such conflicts can be managed effectively. The key to success will be striking a balance between promoting regional integration and respecting the cultural and religious diversity of the member countries, as well as addressing any disparities in readiness and willingness among member states to implement the policy.

The new MABIMS policy criteria as a unique perspective on the Hijriyah calendar is an interesting issue amid various differences of opinion. Approval and disapproval are volatile and potentially collide. This, if not handled properly, can trigger and maintain conflict. The government has tried and selected the MABIMS criteria as a state perspective, which has sparked various reactions from three aspects: acceptance, silence and rejection. The three of them ended up arguing, even in the latest case triggering the reporting of a religious organisation against a person suspected of carrying out hate speech on social media.

What is done by the government by ‘choosing’ the MABIMS criteria with various considerations as an extension of state policy is a necessity, but it is still very important to prioritise dialogue, especially for those who have different views from the government. The positioning that has been taken by the government so far has been on the track by providing sufficient space for differences, and not going as far as to ban things in the name of religious moderation.

In fact, the middle way that has been implemented and continues to be pursued by the government is indirectly welcomed by Muhammadiyah, which has given a positive signal regarding the concept of Hijriyah Calendar Unification. ‘But of course everything needs a long friendship until the Global Islamic Calendar is realized, but we must not lose hope’, said Haedar Nashir, General Chairperson of the Central Executive (PP) Muhammadiyah in the Eid Al-Fitr Gathering 1444 H PP Muhammadiyah at the Yogyakarta Muhammadiyah University Sportorium (UMY) on Sunday (30 April 2023).

It was further stated that the main thing that needs to be encouraged is through silaturrahmi, and the meaning of silaturrahmi in a deeper and broader context. Not just linking brotherhood as its root, namely silah wa rahmi which is ordinary social relations, in the form of greetings, forgiving each other, or ceremonial events. However, how to draw the meaning of silaturrahmi in broader social relations to build a more civilised life. If this is greeted with wisdom and tolerance, of course, it has the potential to be met in a more dynamic dialogue space so that conflicts can be avoided. Mutual respect is important to be encouraged, but it also needs to be in harmony with an attitude of tolerance without feeling that someone has a higher position, knowledge, and authority than the other. Isn’t it conveyed in the rule of law that prioritising avoiding harm is far more important than seeking benefit?

Governments also have an important role to play in facilitating dialogue and formulating policies that take into account multiple perspectives. Using scientific data and a technically accountable approach can help reduce uncertainty and minimise conflict. In addition, education and awareness raising can also help reduce conflict in society. Understanding the differences and the importance of inter-religious harmony can promote mutual understanding and tolerance.