Are Islamic Legacy Calendars of the Lunar Type, Really? Measurement of the Deviation
Rafik Ouared
Abstract
Background and Purpose: This study aims to demonstrate that the so-called Islamic legacy calendars are of the Gregorian-like type far from corresponding to the properties of the synodic lunar month. This unexpected result provided the first stone from which the search for a coherent definition of legacy criterion has been undertaken in this work.
Material and Methods: To this end, distributions of time lag (Δt0), the time distance between the lunar conjunction (LC) and the first lunar day of the month, were processed and used to estimate the 1st−Day rejection index (RI) for four computerized calendar paradigms used in Lausanne city, between1938 and 2038. Those estimates measured the deviations from the lunar synodic properties caused by the underlying hypotheses. In addition, new synoptic figures of the projected 2023/1444H Ramadan calendars in twelve pilot cities were computed to highlight the fundamental reason for mismatch along with specific assessment. Those figures also aimed to illustrate the competitive effects of four environmental parameters on final issues, namely: LC, latitude, time zone and season.
Results: Several results were found: RI was ranging between 45% and 90% while the corresponding rejection thresholds were between 8h and 18h. The synoptic figures, while fully explaining the similarities and differences between the calendars in and between cities with all their respective 1st−Day dates being summarized in “Confusion Tables”, they also contributed to demonstrate that all the residual flaws of the Islamic calendars were caused by explicit and implicit assumptions of unfounded “day reference times” (DRT), as if the lunar context was assimilated to a Gregorian-like one.
Conclusion: The results were finally analyzed within the framework of the “inclusive science approach” (ISA) and a new proposal was made in favor of a “single and universal” Islamic calendar legacy definition, which conforms on the one hand, to the properties of the lunar synodic month and on the other hand, to lunar Islamic requirements.
Full Text: PDF DOI: 10.15640/jisc.v11n1a1
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