According to Article R. 57 of the Electoral Code, the presiding officer of polling stations states the opening and closing times of the ballot in the report on the sorting process. The Supreme Court has considered since 2013 that failing to mention this information constitutes an irregularity justifying in itself annulment of the elections (Cass. soc., 16 October 2013, n° 12-21.680).
In its ruling of 17 December 2014 (Cass. soc., 17 December 2014, n° 14-12.401), the Court agreed that, where a section on the opening and closing times of the ballot fails to appear on standard CERFA forms, said times could be freely noted on a document in appendix to the report on the sorting process.
This ruling now has limited scope since the administrative authorities recently updated the CERFA report forms which now incorporate a section intended for the opening and closing times of the ballot (www.elections-professionnelles.travail.gouv.fr).