Le treize mars - expression of dates in French

Question

In the quiz on revision of A0: Le treize mars means: the thirteenth March was marked wrong and thirteenth of March was marked right answer. I couldn't understand the differences. In one of the examples: Halloween est le 31 octobre: Halloween is October 31. and not as 31st. of October. I fail to understand the differences. Request clarification and correction

Answer

The answer may lie in your question:  I notice that you indicated "the thirteenth March" as being incorrect; however "thirteenth of March" as being the correct answer.  Having looked at the lesson cited above, all of the dates that are used as examples do not translate as "the thirteenth" but as "thirteen of. . ."  
Hope that helps.