Old Postmarks

Just a quick and easy question: I enjoy finding really old and clean postmarks - especially the SON variety - my question is when the postmark says "03 IX 92" is the roman numeral substituting for the month so that the date I mentioned would be September 3, 1892? Or do I have that wrong? Are there any other "shorthand" postmark conventions that I should be aware of?

Thanks

Correctamundo Scouter,
there are anomolies but very scarce.

Another point to bear in mind is that not every country used (or still uses, for that matter) the AD (or CE) calendar.

This cover was not postmarked in 1919



but in June 1944.

You'll find that the years in Japanese postmarks are dated from the beginning of the current Emperor's reign. This means that, to find the AD/CE equivalent, you must add 1867 (for the oldest stamps), 1911 (for older stamps), 1925 (for more modern stamps) and 1988 (for modern stamps). There are other dating systems as well, in China and the the Middle East among others.