Predicted UK Islamic Calendar Dates for 2021 (1442/1443)

Imad Ahmed

Many people have contacted New Crescent Society asking:

Can you give us the dates for the Islamic calendar for 2021, based on local UK moonsighting?

We will provide one in this blog piece. Please note that this is not a definitive calendar, but a predicted one, based on moon visibility data in the UK. A moonsighting-based calendar can only be determined by moonsighting on the day of sighting month on month.

(Before you continue, please do take a read about the problem of the UK calendar, and our proposed solution.)

How has this predicted calendar been calculated?

This predicted calendar is based on UK moon visibility data.

We have looked at this data for the 29^th of each Islamic month, and then:

• If the moon is predicted ‘visible’ in the UK, that month will have 29 days, and the new month will now begin.
• If the moon is predicted ‘not visible’ in the UK, that month will have 30 days, and the new month will begin a day later

Further notes on the data used:

• The visibility data is taken from Her Majesty's Nautical Almanac Office (HMNAO) which is historically part of the Royal Observatory Greenwich.
• HMNAO grade new crescent visibility with a code: A, B, C, D, E and F. An 'A' code means easily visible this month, and an 'F' code means impossible to see.
• In our experience, the moon is only practically visible in the 'A' code; it is visible the 'B' code when the moon is older than 24h. This is also the practical experience of the astronomers who work for Morocco's government, based on over 40 years of collecting moonsighting data. Thus this is the measure we’ve used to determine what constitutes predicted ‘visibility’, and is so far accurate to our experience of the moon in the UK.
• We have highlighted all of the occasions this year where it may be challenging, but still possible, to see the moon. It will be challenging because these moons are predicted to be particularly thin, and low on the horizon. We have offered some additional notes in the table below.
• In this predicted calendar, we have assumed that the moon will be seen if the data suggests that the moon is visible, even if it is a 'challenging' moon that month. 

What if the moon isn’t seen? Notes on cloudy weather:

It is possible that it is cloudy on any given month, irrespective of the predicted visibility of the moon, and it is not seen on any given month. Clouds can make it difficult for us to observe the sun, let alone a thin crescent moon!

Thus, any predicted 29 day month below may become a 30 day month. This is perfectly normal in an Islamic calendar.

What normally happens is that the next month that was going to have 30 days will have 29 days instead. 

Example:

• We have predicted Rajab will have 29 days, and Shaban will have 30 days.
• However, if it is cloudy and Rajab ends up with 30 days, we would expect Shaban to have 29 days instead. 

Again, this is perfectly normal in the Islamic calendar.

In general our moonsighting in the UK has improved to the point that cloudy weather has not prevented us from seeing the moon month on month, and the weather has not proved a problem per se.

However, there are some moons in 2021 (1442/1443) which are more easily visible in parts of the country, yet extremely challenging in other parts of the country, which makes it quite tricky to predict with certainty if the moon will be seen or not. What’s more, only God knows about what the weather will be like in the UK for the coming year, and as such, we would expect some adjustments to occur to the below calendar. To give you a sense, we've made about one adjustment per year over the last three years, compared to our predicted calendar.

Ultimately our belief is that this is a fairly accurate predicted calendar for the lunar visibly calendar in the UK, insha allah, but no moonsighting based Islamic calendar can ever be 100% predicted.

Compiled by: Imad Ahmed, New Crescent Society.

NOTE: I sent this calendar with the data out to a number of experienced moonsighters. Some had some slight disagreements with me - namely, they have assumed that the moon will not be seen for Rabi al Awwal and Jumada al Ula on the 29th of their respective previous months, as the moon is very difficult to sight in parts of the UK / Scotland. Only time will tell. 🌙💫

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