I have found a reference to the 'Blessing for the sun' that occurs every twenty eight years, the last being in 1981 CE so the next should be in 2009. Could you tell me the source of the blessing for the sun, as I am unable to find more than scant references to it.

Answer

The source for the sun blessing every 28 years is from Talmud Brachot 59b.

Additional sources - "Maimonides" Laws of Blessings 10:18; "Code of Jewish Law" O.C. 229:2.