Hebrew date conversion for London, 17Century…..While analyzing the accounts for the Creechurch Lane synagogue in 5436-37 (1676-77) there are more than 6 account book entries dated Hesuan 30 in year 5437. This is confusing as:Hebcal, Chabad, and Torahcalc all return 29 days for Hesuan.Chat GPT responded with 30 days given that: “*Year 5437 was also a regular year (non-leap year) but was classified as shlemah (complete). In a shlemah year, Heshvan has 30 days.”*When ChatGPT was asked about the difference between its answer of 30 days and 29 days returned by commonly used date converters, ChatGPT consulted Hebcal and changed their answer to 29 days.With multiple account book entries of Hesuan 30, the synagogue believed that this was true. Is it possible that there is another explanation for this discrepancy?