I have a graph that plots date along the X-axis and financial figures on the Y.

The trend line plots particular figure on the date given. So far so good.

The dates are not evenly spaced, ie the figure is not taken regularly every x days/weeks, so the x-axis labels are evenly spaced rather than spaced according to time between them.

Still with me?

Now, how do I persuade OpenOffice (or Excel) graphing tools to recognise the x-axis data labels are dates and that I want them spaced according to time between them?

Have you formatted the data cells themselves to 'date' or are they set as text? I would have thought formatting them to date would work?

In Excel, if you enter the dates as dates, the graph will recognise this and plot accordingly.

The cells are formatted as dates, yes.
I copy/pasted the sheet into Excel (from OpenOffice) and it recognised the dates and spread the plot out as I hoped automagically.

So it's an OpenOffice query now then...

Too late, wrote a post all about Excel, I know nothing about Openoffice!