Pieter wrote...
as time values for a graph, how can I get these accepted as dates to plot
data for a time series for, let's say, housing prices between 1750 and
2005?
Unless you're plotting daily house prices, you don't need to use dates.
So don't. Enter years and housing prices as simple numbers, and plot as
X-Y scatter charts. If you need to include month names, enter year and
month as text and housing prices as simple numbers, and plot as a line
chart.
It's possible to manipulate date *strings* prior to 1900, but they'll
*always* be text, so they'll screw up X-Y charts but not line charts.