Using copy and paste I transferred the trendline equation (in this case a
quadratic) from a chart element to a worksheet cell and then subjected it the
original data to validate it. The resulting values are magnitudes different
to the orignal data - in the millions, not explained by regression tolerance,
RHO of 0.998. The x axis values were months - what value does Excel assign to
months in Charts because the 1900 system values (eg 39643 for 14 Jul 2008) do
not appear to be ones used?