Also, AD / BC wasn't devised until 525 AD, and zero was common at that point, so that can't be the reason: https://en.wikipedia.org/wiki/Anno_Domini
EDIT: Apparently I'm wrong :)
Neither the concept nor a symbol for zero existed in the system of Roman numerals. The Babylonian system of the BC era had used the idea of "nothingness" without considering it a number, and the Romans enumerated in much the same way. Wherever a modern zero would have been used, Bede and Dionysius Exiguus did use Latin number words, or the word nulla (meaning "nothing") alongside Roman numerals.[1][3][4] Zero was invented in India in the sixth century, and was either transferred or reinvented by the Arabs by about the eighth century. The Arabic numeral for zero (0) did not enter Europe until the thirteenth century. Even then, it was known only to very few, and only entered widespread use in Europe by the seventeenth century.
There is also social housing, build in the 16th century by one of the top 3 wealthiest people in modern history. Still in use today, about 1€ a year rent.