If it's just two date ranges you want to represent, then you can set the cut-off date in options. Any date before the cutoff will then be represented by a hollow dot; any date after a solid dot. Or you could do it manually; i.e., you could do two reports filtered by date, then add the results to the map. Once the reports are added to the map, then you can colour the dots as you please.

Beyond this, your best bet would be to use DMAP and Recorder's DMAP export capabilities.

http://www.dmap.co.uk/