Sorry, I don't buy that explanation. Most of the time Wan Phra falls on the specified moon phase. Now and then it's a day off. This is the first time I've noticed it being two days off.
Do you have a reference that points to that frozen-in-time calendar?
Full Moon, Chinese New Year and Wan Phra
Re: Full Moon, Chinese New Year and Wan Phra
If we take Vesak Day, for example, which occurs on the Full Moon, this year it is celebrated in Thailand on 1st June, which was a full moon in 8000 BC. However this year the actual full moon will be on 2nd June.
Re: Full Moon, Chinese New Year and Wan Phra
Here's the answer, stated quite simply:
So, it has nothing to do with ten thousand year old calendars "fixed in time" and has everything to do with archaic methods of calculating calendar dates and phases of the moon.
This is not unlike the ancient Julian Calendar which resulted in poorly calculated dates in the Christian world and which was replaced by the Gregorian Calendar.
From: Wikipedia - Buddhist CalendarWaxing and waning[edit]
The days of the month are counted in two halves, waxing and waning. The 15th of the waxing is the civil full moon day. The civil new moon day is the last day of the month (14th or 15th waning). Because of the inaccuracy of the calendrical calculation systems, the mean and real (true) New Moons rarely coincide. The mean New Moon often precedes the real New Moon.
So, it has nothing to do with ten thousand year old calendars "fixed in time" and has everything to do with archaic methods of calculating calendar dates and phases of the moon.
This is not unlike the ancient Julian Calendar which resulted in poorly calculated dates in the Christian world and which was replaced by the Gregorian Calendar.