Where the dates come from
The dates and times of every new moon, first quarter, full moon and last quarter in 2027 come from the US Naval Observatory’s Astronomical Applications service. We checked them against Fred Espenak’s NASA phase table: 47 of 49 match to the minute, and the other two differ by one minute without changing the date. Times are converted to UK time, with British Summer Time from 28 March to 31 October 2027 (GOV.UK). Two phases fall on a different date in the UK than in UTC: the new moon of 7 April (00:51 BST) and the full moon of 16 September (00:03 BST).
How each day gets its colour
With 8 colours, the day of each principal phase gets that phase’s colour, and the days in between take the colour of the stretch they’re in: waxing crescent, waxing gibbous, waning gibbous or waning crescent. That gives 13 new moon days, 12 of each other phase, and 78 to 81 days for each in-between colour. The “how much is lit” option uses the Naval Observatory’s percentage of the moon lit at noon in London on each day.
The full list of 2027 phases in UK time, and how published moon blankets are made, is in our moon phase blanket 2027 guide.