There really will be a full moon on Christmas this year, just like in the John Lewis ad.

The short video — which features a young girl who makes friends with a man who lives on the moon — revolves around the visibility of the satellite at Christmas. And it really will be clear: a full moon will fall exactly on Christmas Day.

The full moon hasn’t fallen on Christmas Day since 1977, and won’t come back for another 19 years.

Of course, the chance of the full moon falling on Christmas is the same as every other day: it will happen twice every 59 years. But we have been in a particularly bad patch for Christmas full moons in recent years.

The full moon will occur at 11.11 GMT on 25 December. That will actually mean that it won’t technically be full in the US, where it will be closest on Christmas Eve.

The last time the moon being full on Christmas was celebrated was 2004. But that wasn’t entirely true — the full moon really fell on 26 December, and it just looked full on Christmas day. The same thing happened in 2007, when it fell on Christmas Eve.

The most recent really full moon on Christmas day was 1977.

Full moons sometimes get in the pattern of appearing on a specific date every 19 years. The date falls in and out of that period of repetition, and we’ve been out of one for years.

But with this year’s full moon, the repetitions begin. After 2015’s full moon, the next ones will come in 2034, 2053 and 2072.

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