Nowruz in the Twelver Shi’a faith
Twelver Shi’a hold the day of Nowruz in high regard. The day upon which Nowruz falls has been recommended as a day of fasting for Twelver Shi’a Muslims by Shi’a scholars, including Imam Khomeini, Abul-Qassim al-Khoei, and Ali al-Sistani. The day also assumes special significance for Shias as it was on 21 March 656 AD when the first Imam Hazrat Ali (A.S) assumed the office of Caliphate.
Source: encyclopedia.thefreedictionary.com