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 predicted by the Umm al-Qura calendar.
Since 1419 AH (1998/99 CE) 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. However, the religious authorities of Saudi Arabia also allow the testimony of less experienced observers and thus sometimes announce the sighting of the lunar crescent on an evening when none of the official committees could observe the lunar crescent or even on an evening when the lunar crescent actually set before sunset.
This often leads to confusion when the dates of important religious events in Muḥarram, the month of fasting (Ramaḍān) or the month of pilgrimage (Dhu ʾl-Ḥijja) are changed. In nearly all of these cases, a retrospective analysis indicates that these extremely early reports of the lunar crescent are impossible and were based on false sightings. Most of these false sightings were probably caused by a bright star or planet (such as Venus) or an airplane contrail viewed near to the western horizon.
A study of 42 reports of sightings of the Ramaḍān new moon, as announced by the High Judiciary Council of Saudi Arabia (Majlis al-Qadāʾ al-Aʿlā) between 1962 to 2001 (1381 AH to 1422 AH), confirms that more than half of these were too early and based on false sightings of the lunar crescent (Kordi, 2003). A similar result was reached by a later study covering the years 1380 AH to 1425 AH (Gadi, 2007).
The following table compares the Umm al-Qura dates for the begin of the months Muḥarram, Ramaḍān, Shawwāl and Dhu ʾl-Ḥijja with the dates announced by the High Judiciary Council of Saudi Arabia (source: Fatwa-Online):
year | 1 Muḥarram | 1 Ramaḍān | 1 Shawwāl | 1 Dhu ʾl-Ḥijja | 10 Dhu ʾl-Ḥijja | |||||
computed | announced | computed | announced | computed | announced | computed | announced | computed | announced | |
1422 | 26 Mar 2001 | 16 Nov 2001 | 16 Nov 2001 | 16 Dec 2001 | 16 Dec 2001 | 13 Feb 2002 | 13 Feb 2002 | 22 Feb 2002 | 22 Feb 2002 | |
1423 | 15 Mar 2002 | 6 Nov 2002 | 6 Nov 2002 | 5 Dec 2002 | 5 Dec 2002 | 2 Feb 2003 | 2 Feb 2003 | 11 Feb 2003 | 11 Feb 2003 | |
1424 | 4 Mar 2003 | 26 Oct 2003 | 27 Oct 2003 | 25 Nov 2003 | 25 Nov 2003 | 23 Jan 2004 | 23 Jan 2004 | 1 Feb 2004 | 1 Feb 2004 | |
1425 | 21 Feb 2004 | 15 Oct 2004 | 15 Oct 2004 | 14 Nov 2004 | 13 Nov 2004 | 12 Jan 2005 | 11 Jan 2005 | 21 Jan 2005 | 20 Jan 2005 | |
1426 | 10 Feb 2005 | 4 Oct 2005 | 4 Oct 2005 | 3 Nov 2005 | 3 Nov 2005 | 1 Jan 2006 | 1 Jan 2006 | 10 Jan 2006 | 10 Jan 2006 | |
1427 | 31 Jan 2006 | 24 Sep 2006 | 23 Sep 2006 | 23 Oct 2006 | 23 Oct 2006 | 22 Dec 2006 | 21 Dec 2006 | 31 Dec 2006 | 30 Dec 2006 | |
1428 | 20 Jan 2007 | 13 Sep 2007 | 13 Sep 2007 | 13 Oct 2007 | 12 Oct 2007 | 11 Dec 2007 | 10 Dec 2007 | 20 Dec 2007 | 19 Dec 2007 | |
1429 | 10 Jan 2008 | 1 Sep 2008 | 1 Sep 2008 | 1 Oct 2008 | 30 Sep 2008 | 29 Nov 2008 | 29 Nov 2008 | 8 Dec 2008 | 8 Dec 2008 | |
1430 | 29 Dec 2008 | 22 Aug 2009 | 22 Aug 2009 | 20 Sep 2009 | 20 Sep 2009 | 18 Nov 2009 | 18 Nov 2009 | 27 Nov 2009 | 27 Nov 2009 | |
1431 | 18 Dec 2009 | 18 Dec 2009 | 11 Aug 2010 | 11 Aug 2010 | 10 Sep 2010 | 10 Sep 2010 | 7 Nov 2010 | 7 Nov 2010 | 16 Nov 2010 | 16 Nov 2010 |
1432 | 7 Dec 2010 | 1 Aug 2011 | 1 Aug 2011 | 30 Aug 2011 | 30 Aug 2011 | 28 Oct 2011 | 28 Oct 2011 | 6 Nov 2011 | 6 Nov 2011 | |
1433 | 26 Nov 2011 | 27 Nov 2011 | 20 Jul 2012 | 20 Jul 2012 | 19 Aug 2012 | 19 Aug 2012 | 17 Oct 2012 | 17 Oct 2012 | 26 Oct 2012 | 26 Oct 2012 |
1434 | 15 Nov 2012 | 9 Jul 2013 | 10 Jul 2013 | 8 Aug 2013 | 8 Aug 2013 | 6 Oct 2013 | 6 Oct 2013 | 15 Oct 2013 | 15 Oct 2013 | |
1435 | 4 Nov 2013 | 5 Nov 2013 | 28 Jun 2014 | 29 Jun 2014 | 28 Jul 2014 | 28 Jul 2014 | 25 Sep 2014 | 25 Sep 2014 | 4 Oct 2014 | 4 Oct 2014 |
1436 | 25 Oct 2014 | 18 Jun 2015 | 18 Jun 2015 | 17 Jul 2015 | 17 Jul 2015 | 14 Sep 2015 | 15 Sep 2015 | 23 Sep 2015 | 24 Sep 2015 | |
1437 | 14 Oct 2015 | 15 Oct 2015 | 6 Jun 2016 | 6 Jun 2016 | 6 Jul 2016 | 6 Jul 2016 | 2 Sep 2016 | 3 Sep 2016 | 11 Sep 2016 | 12 Sep 2016 |
1438 | 2 Oct 2016 | 2 Oct 2016 | 27 May 2017 | 27 May 2017 | 25 Jun 2017 | 25 Jun 2017 | 23 Aug 2017 | 23 Aug 2017 | 1 Sep 2017 | 1 Sep 2017 |
1439 | 21 Sep 2017 | 21 Sep 2017 | 16 May 2018 | 17 May 2018 | 15 Jun 2018 | 15 Jun 2018 | 12 Aug 2018 | 12 Aug 2018 | 21 Aug 2018 | 21 Aug 2018 |
1440 | 11 Sep 2018 | 11 Sep 2018 | 6 May 2019 | 6 May 2019 | 4 Jun 2019 | 4 Jun 2019 | 2 Aug 2019 | 2 Aug 2019 | 11 Aug 2019 | 11 Aug 2019 |
1441 | 31 Aug 2019 | 31 Aug 2019 | 24 Apr 2020 | 24 Apr 2020 | 24 May 2020 | 24 May 2020 | 22 Jul 2020 | 22 Jul 2020 | 31 Jul 2020 | 31 Jul 2020 |
1442 | 20 Aug 2020 | 20 Aug 2020 | 13 Apr 2021 | 13 Apr 2021 | 13 May 2021 | 13 May 2021 | 11 Jul 2021 | 11 Jul 2021 | 20 Jul 2021 | 20 Jul 2021 |
1443 | 9 Aug 2021 | 10 Aug 2021 | 2 Apr 2022 | 2 Apr 2022 | 2 May 2022 | 2 May 2022 | 30 Jun 2022 | 30 Jun 2022 | 9 Jul 2022 | 9 Jul 2022 |
1444 | 30 Jul 2022 | 30 Jul 2022 | 23 Mar 2023 | 23 Mar 2023 | 21 Apr 2023 | 21 Apr 2023 | 19 Jun 2023 | 19 Jun 2023 | 28 Jun 2023 | 28 Jun 2023 |
1445 | 19 Jul 2023 | 19 Jul 2023 | 11 Mar 2024 | 11 Mar 2024 | 10 Apr 2024 | 10 Apr 2024 | 7 Jun 2024 | 7 Jun 2024 | 16 Jun 2024 | 16 Jun 2024 |
1446 | 7 Jul 2024 | 7 Jul 2024 | 1 Mar 2025 | 30 Mar 2025 | 28 May 2025 | 6 Jun 2025 |
In ten cases (Ramaḍān 1424 AH, Muḥarram 1433 AH, Ramaḍān 1434 AH, Muḥarram & Ramaḍān 1435 AH, Dhu ʾl-Ḥijja 1436 AH, Muḥarram & Dhu ʾl-Ḥijja 1437 AH, Ramaḍān 1439 AH and Muḥarram 1443 AH) the lunar crescent was first sighted on the evening after the evening predicted by the Umm al-Qura calendar.
However, in seven cases (Shawwāl & Dhu ʾl-Ḥijja 1425 AH, Ramaḍān & Dhu ʾl-Ḥijja 1427 AH, Shawwāl & Dhu ʾl-Ḥijja 1428 AH and Shawwāl 1429 AH) the lunar crescent was supposedly first sighted on the evening before the evening predicted by the Umm al-Qura calendar with moonset occurring just before or even well before sunset.
In some cases the advancement of the month can result in a month length of 31 days which is awkward as Islamic tradition only allows for month lengths of 29 or 30 days. In such cases one of the days in the month is reckoned twice. For instance, both Friday 28 December and Saturday 29 December 2007 were reckoned as 19 Dhu ʾl-Ḥijja 1428 AH.