Tax time
The online filing deadline depends on the département. The paper deadline is earlier. The official calendar for the year gives the days. Next year's dates are published only in the spring.
Accounts opened abroad are declared separately, including an account whose IBAN does not start with FR. The official page states the penalty.
Who files, and when, from service-public.fr. Income tax return
Source: service-public.fr
The official tax calendar, month by month. Tax calendar
Source: impots.gouv.fr
Declaration of accounts opened outside France (form 3916). Accounts abroad
Source: service-public.fr