Latitude's default location history map and KML export will only give you one day at a time. This tutorial helps you work around the limit to view your entire location history in Google Earth or another map viewer.
(Thanks to Ask Metafilter for the tip.)
Choose today or a different end date.
With the end date selected, right-click the "Export to KML" link and select "Copy Link Address".
Paste that link address into a text editor.
Change the default start date (which will be about 24 hours before the end date) to some much smaller number:
Paste the modified URL into your browser, hit Enter, save the KML file.
Load the KML file into Google Earth or another map viewer.