What should be the return due date

Mohan Kale (376 Points)

28 December 2021  
An education instituition (trust) incurred loss in FY 2020-2021 and claims exemption u/s.10(23C)(iiiad), requires audit under Bombay Charitable Trust Act. What would be the due date for filing return of income? Whether 31St December or 15th February?