Wouldn't the rotation of the earth's axis over 26,000 years cause a change in where the sun set relative to the temple. If I am correct, then he should be able to calculate when the sun would have risen in the correct place and calculate the date of the temple.
I also discovered some interesting references to Dilman in Gloria Farley's book "In Plain Sight: Old World Records in Ancient America" regarding correlation between certain sacred images in Dilman and some found in "amerindian" sites in the USA.
Read it, good book.