Earliest possible date for a post in WordPress … how about 1858?

Hi there,
I am contemplating using WordPress as a tool to create and display my family history. I already use it for my family’s blog, and have realised that really what I am doing is creating our family history: picture, sories and dates, for the last 2 years. Now I am thinking about bringing my WHOLE family history into wordpress, with stories post – dated, and using categories for things like people’s names and so on. My earliest post, using this method, would be from 1858, when Charles Thorpe migrated from blighty to South Australia.

SO .. what is the earliest date WordPress will recognise? I did a short test and it seemed like in some places WP recognised the 1858 date, and in others, the date became 1963.