There are a lot of buildings near where I live that have the date they were built carved in the stone in roman numerals. I was interested enough, when a teenager, to find out what they meant. I'm not sure how much of it I can remember now.
M = 1000, D= 500, C = 100 L = 50m X = 10m V = 5, I = 1.
The strange ones are things like 4 is IV ie one before 5. 40 = XL - 10 before 50.
I think 2011 is MMXI
The local Methodist chapel was built in MDCCCLIV