After 17 years restoration Prasat Phanom Rung was finally re-built from ruins in 1988. The name was changed to Phanom Rung Historical Park and the traditional annual lunar festival was changed to a solar and fixed to a date in the beginning of April, when the rays of the rising sun penetrates the 15 doorways of the sanctuary. The old festival followed the full moon in April which falls on different dates in succeeding years, but the solar event fall on the same date in the beginning of April – some years differing 1 day.
The reason for this change was probably due to that an archaeologist observed the sun rise through the doors of the temple during the restoration of the temple. This should not have surprised anybody: With a few exceptions all Khmer temples are orientated so that the rays of the rising sun enter the eastern doors on two occasions a’ year. Prasat Phanom Rung only differs from other temples in Isan on two matters: 1: The sanctuary has western doors as well, thus allowing the rays of the sun to penetrate the construction when the (not re-constructed) wooden doors were opened. 2: The temple is beautifully located of a mountain top.
Until 2004 only one solar event was taken into consideration: The sunrise in April. Actually there are four solar events; the other three are a sunrise in September and two sunsets in March and October as described in an article by the author in Bangkok Post, March 2000, after an observation of the sunset through all 15 doorways the 7th of March 2000: New Light on an Ancient Site.
The article did not change the annual festival until 3 years after, when the author invited the director of Phanom Rung Historical Park, Nongkram Suksom, to watch the sunset in March 2003. Next day the governor of Buriram province was present and luckily the sun broke through the clouds just before reaching the horizon. This impressed the governor to an extend that the month from the sunset in March 2004 to the sunrise in April was declared for ''The Holy month of Prasat Phanom Rung'' and rituals were preformed at both occasions.