Maybe saying that there are as many date-writing conventions as countries in the world is a bold exaggeration, but it’s not that far from the truth. The Polish way of writing dates isn’t very different from how it’s done in the English-speaking world, but you might want to pay attention to some important details – that is, if you really want to be fully correct. Not that all native speakers are, of course…
First of all, looking at Polish dates, you might have noticed the lonely r. that often appears after the year: 13.12.1987 r. It’s an abbreviation of the word rok, meaning year. If you’re reading this aloud, though, you have to put this word in the Genitive case: roku. And yeah, there’s a full stop after the r. Don’t omit it.
Is this r. compulsory? No, but it’s very common, and many people put it there out of habit.
Secondly, brush up on your Roman numerals, as they are often used to write the month. For example, the previous example can be written as 13 XII 1987 r. Again, this is mostly a matter of habit – I got used to it in school, for example – not something you have to do. This convention is very useful, though, since it obviates any ambiguity that can emerge if both the day and the month are written with Arabic numerals.
Thirdly, remember the punctuation – this is where many people make mistakes. You probably noticed the difference in the examples above. If you write everything with Arabic numerals, you put full stops after the day and the month. You don’t put them there if you’re using a Roman numeral (apart from the full stop after the r. of course).
Finally, if you’re familiar with the Polish months and their declination, you can write out the month. Why do I mention declination? Because you have to put the month in the Genitive case. As for the punctuation, you don’t use full stops here either. For example:
10 stycznia 1999 r.
10 I 1999 r.
10.1.1999 r.
1 października 2004 r.
1 X 2004 r.
1.10.2004 r.