Different languages have different conventions. For example, the standardized variety of my language allows 11/(0)9/2001, 11/(0)9/01, 11.(0)9.2001, 11.(0)9.01, 2001-09-11, 2001/09/11, 2001.09.11 (personally I usually use 11/09 without the year and 2001-09-11 with the year).
Different languages have different conventions. For example, the standardized variety of my language allows 11/(0)9/2001, 11/(0)9/01, 11.(0)9.2001, 11.(0)9.01, 2001-09-11, 2001/09/11, 2001.09.11 (personally I usually use 11/09 without the year and 2001-09-11 with the year).