@George4Tacks is correct that FBAR is due Apr 15 but may be extended under the same rules as income tax return to Oct 15.  However, no extension needs to be filed as the FinCEN would grant the extension automatically each year to taxpayers who fail to meet the Apr 15 deadline in order "to implement the statute with minimal burden".

This has been the policy since the FBAR filing deadline was changed by the Surface Transportation and Veterans Health Care Choice Improvement Act of 2015.

https://bsaefiling.fincen.treas.gov/FFBARHelp.html