April 20

Regarding the beginning of the Zoroastrian era, in one of His Tablets 'Abdu'l-Bahá states that Zoroaster lived about 750 years after Moses. In a letter to an individual believer the Guardian's secretary wrote on his behalf: "Zoroaster lived about a thousand years before Christ. There is no exact date in the teachings regarding the beginning of His Dispensation." 
(From a letter dated 13 May 1979 written on behalf of the Universal House of Justice to an individual believer)