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Ramadan: What does the New Moon have to do with Ramadan?
Image source, Getty Images
People across the world have been looking out for the Crescent Moon - or New Moon - to see when the religious holy month of Ramadan begins.
Ramadan is a very important time in the Islamic calendar, and Muslims all over the world will be preparing to take part.
The holy month can start and end on different dates depending on the year, and on where you live.
It's all to do with whether people have been able to see the New Moon, which is when the moon is in a very thin crescent shape (if you're not sure what a crescent is, it's the shape above!).
Why do you need to see the New Moon to start Ramadan?
Image source, Getty Images
Going back hundreds of years ago, it was harder to keep track of dates to start celebrations.
So the calendar often relied on the movement of the Sun, Moon and Stars.
The Islamic calendar uses the New Moon to signal the start of the month - something which is particularly important during the month of Ramadan because people need to know when to start and stop fasting.
Has Ramadan started in the UK and across the world?
Image source, Getty Images
This year Ramadan officially started on 23 March in the UK, but that's not the case everywhere in the world.
In many countries people saw the new Crescent Moon on 22 March which meant Ramadan began on 23 March.
But in some countries the moon wasn't seen.
In India, Ramadan will start on 24 March because the moon hasn't been seen there yet.
In the UK a special programme looking for the moon was broadcast by the Royal Observatory, a place which has lots of huge telescopes to look into space.
Imad Ahmed, from Islamic group the New Crescent Society, was on the programme, and said: "The Sun, the stars, the Moon, the sky are a natural source of wonder."
He said those things hold important meaning to religions including Islam because it's "related to a sense of spirituality" which makes people feel closer to God.
The new moon is important, he said, because "it determines when we begin the fast - because it determines when the month begins - and determines when the next month begins which is when we end the fast."