The GetVersions() call to the Versions.asmx web service in SharePoint 2003 returns a localised date format, with no way of determining what the format is. It's the site regional setting of date format, but I can't find a way to get even that out of SharePoint 2003. Locally, it looks like SPRegionalSettings can be used (http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.spregionalsettings.aspx) but what about a web service version of this?
Unfortunately, the parameter that asks for the values in UTC is not supported for this call. I've just had to look for a month greater than 12 and use that as the hint to switch date formats. It'll mess up some dates, but I can't see a way around that. The code is at http://sourceforge.net/projects/splistcp/ if anyone is interested.