"on the 5th of November" is practically just removing the word day from the reference. As in "on the 5th (day) of November." It is used everywhere and even though it could be understood a few different ways it is the most correct. "on the 5th November" seems to me to more be dependent on the month and if not year.

Understanding the Context

As in "it's my baby's 5th November" as in, the child is experiencing November ... grammar - When referring to dates, which form is correct? "on the 5th ... "5th May" would be the most traditional way to write this date.

Key Insights

I have never seen "of" used in a written date, except in extremely archaic constructions such as legal contracts "signed and witnessed this 5th day of May 2012" (Parenthetically, I note that in English law this makes absolutely no difference to validity. 5 I would read it as "4 out of 5", meaning there are 5 of something and this is the 4th (maybe the 4th best, maybe the 4th one chronologically) of them. An equally valid reading would be "4 or 5" meaning this is either the 4th or 5th of an undetermined number of things (or baby mommas). Capitalisation implies that the name has been elevated to have meaning in its own right, not just as a literal description. For example, if the mezzanine between the 1st and what was the 2nd floor was converted to be the 2nd floor, what had been the 4th floor would become the 5th floor but might be referred to as "the 4th Floor".

Final Thoughts

Similarly, say a company owned two bookstores, and in the ... Possibly worth mentioning the commonly accepted - but incorrect - belief that the insertion of Julius and Augustus Caesar's months bumped the 7th-10th months up by two. Especially as the months that were replaced by July and August were 'Quintillis' and 'Sextillis' with obvious links to their 5th and 6th positions in the previous calendar. 5 It is necessary for me to write about the 2.5th and 97.5th percentiles of a data set. What is the correct way of writing this? This post talks about "zeroth", "n-th" and even "epsilonth" as generalisations of the -th suffix, but I haven't found any guidelines for non-integers.

I feel that 2.5th percentile sounds better than 2.5-percentile. Here is something I was able to discover on the internet the prime time I confronted the same predicament as you. 1st = primary 2nd = secondary 3rd = tertiary 4th = quaternary 5th = quinary 6th = senary 7th = septenary 8th = octonary 9th = nonary 10th = denary 12th = duodenary 20th = vigenary. These come from the Latin roots.