At the moment there is no way to insert the system date in a SendKeys statement. Currently, Hotkeys 2000 is under development that will have a lot of enhancements (including sending date and time in a sendkeys statement).
I expect to be able to release the first beta of Hotkeys 2000 before the end of this month. If you're interested in receiving the beta-version of Hotkeys 2000, send mail to hotkeys-beta@broeze.com and I'll add your name to the distribution list.