Indonesian Political, Business & Finance News

Why Eid al-Adha is Confirmed Earlier Than Eid al-Fitr?

| Source: DETIK Translated from Indonesian | Regulation
Why Eid al-Adha is Confirmed Earlier Than Eid al-Fitr?
Image: DETIK

Every year, Eid al-Adha is celebrated on the 10th of Zulhijjah. In Indonesia, the determination of Eid al-Adha typically coincides with the official declaration of the start of Zulhijjah through the sidang isbat.

The Meteorology, Climatology, and Geophysics Agency (BMKG) states that the start of the Hijri month is determined each 29th day via:

  • Hisab: A method using solar and lunar movement data and formulas to calculate the potential visibility of the crescent moon.

  • Rukyat: A sky observation method to confirm whether the crescent is actually visible.

The results of both methods are then discussed in the Ministry of Religious Affairs’ sidang isbat.

MABIMS Crescent Moon Criteria

Citing BMKG’s official Instagram account @infobmkg, Indonesia uses the MABIMS criteria to assess crescent visibility. The crescent is deemed visible if:

  • Minimum altitude of 3 degrees

  • Minimum elongation (angular distance between the Moon and Sun) of 6.4 degrees

If the criteria are not met, the crescent is considered not visible.

Why Eid al-Fitr is Often Announced Late

Eid al-Fitr falls on the 1st of Shawwal, requiring the government to confirm the start of Shawwal to determine the holiday. However, this confirmation occurs on the 29th of Ramadan after sunset, meaning the final announcement can only be made in the evening.

Why Eid al-Adha Can Be Predicted Earlier

Unlike Eid al-Fitr, Eid al-Adha is observed on the 10th of Zulhijjah, not the 1st. Therefore, the sidang isbat determines the start of Zulhijjah (1st), and once confirmed, the 10th is simply calculated. This is why Eid al-Adha can be predicted earlier than Eid al-Fitr.

BMKG’s Role in Crescent Observation

BMKG assists in calculating:

  • Moon and Sun positions

  • Crescent altitude

  • Moon age

  • Lag: the time difference between Moonset and Sunset

  • Illumination fraction: the portion of the Moon illuminated by the Sun

  • Elongation: angular distance between Moon and Sun

  • Weather and cloud cover

  • Crescent visibility probability

  • Sky brightness during observation

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