When to use "the" before a date?
I came across the following sentence:
It dates back to the 6th century BC.
When I looked up when to use the before dates, I read an example sentence from Cambridge Grammar online resources. It says it is correct to write :
Today is the 7th September
Avoidably I am confused when to use the with dates and what does it mean? It is about style?
PS : I know there is already a bit confusion or maybe we can call it varieties of writing dates in terms of format because of regional differences and how to write a date was asked before so I will assume the following formats are standard ones. However, if you think the use of the is part of varieties of writing dates, you can include this point with giving different formats.
American English : September 7, 2016
British English : 7 September 2016
There is another thread asked regarding this issue on ELL but the answer is not enough , when we compare it with Cambridge Grammar online resources
There is another thread on ELU on general rules of writing formats.