You're not supposed to parse those files by yourself. But well, if you want, here's the function which parses the CodeSite message timestamp (based on the TCodeSiteMessage.SetAsString method timestamp parsing code, CodeSite version 5.3.2):
function CodeSiteTimeStampToDateTime(const Value: string): TDateTime;
var
P: Integer;
T: TTimeStamp;
begin
P := Pos('.', Value);
if (P > 0) and TryStrToInt(Copy(Value, 1, P - 1), T.Date) and TryStrToInt(Copy(Value, P + 1, 20), T.Time) then
Result := TimeStampToDateTime(T)
else
raise Exception.Create('Invalid timestamp value.');
end;
Of course this is a CodeSite internal implementation and may be subject to change.