July 30

With reference to your question in connection with the observance of Baha’i Holy Days; the Baha’i day begins and ends at sunset. The night preceding a Holy day is therefore included in the day, and consequently work during that period is forbidden. 
- Shoghi Effendi  (From a message dated July 17, 1937 written on behalf of Shoghi Effendi; ‘Dawn of a New Day’)