Updated July 2022.
Although the moon takes 27.3 days to orbit the earth it takes 29.5 days to complete its phases (because the earth is moving too). This makes it a bit tricky to nail down exactly on which date a full moon occurs, even in the lunar calendar. To cope with this some lunar months are 29 days and some are 30 days. In the wash-up the full moon usually occurs on the 15th or 16th day of each lunar month but not always.
In addition, some years have thirteen full moon festivals, not twelve, if the first of these falls on the first day of the month and the month has 31 days. In 2023 for example, there is a full moon lantern festival in Hoi An on 1 July and 31 July.
For the Hoi An Full Moon Lantern Festival the organizers have taken some of the complications away and the celebration occurs on the 14th day of the lunar calendar, regardless of when the full moon actually occurs.
Thus, in the Gregorian Calendar, the festival occurs on the following dates:
Full Moon Lantern Festival Dates
|16 January||5 January||24 January|
|14 February||4 February||23 February|
|16 March||5 March||23 March|
|14 April||4 April||22 April|
|14 May||3 May||21 May|
|12 June||1 June||19 June|
|12 July||1 July & 31 July||19 July|
|11 August||29 August||17 August|
|9 September||28 September||16 September|
|9 October||28 October||16 October|
|7 November||26 November||14 November|
|7 December||26 December||14 December|