Hello,
Q1 : The main point is that I cannot realize if the displayed date of virus definitions is up-today or not.
In your case, since all the clients are Managed clients, these clients take updates from the SEPM.
Check the SEPM, if the downloads are up to date by following steps
1) SEPM >> HOME>> Windows Definitions dates shows >> "Latest from Symantec" and "Latest on manager"... these both dates have to be the same.
If they are same, then your SEPM is updated.
2) Check the SEPM Liveupdate Downloads
SEPM >> Admin >> System >> Highlight server and click on "Show Liveupdate Downloads"
3) Check this Symantec Website to verify if the updates are Latest:
http://www.symantec.com/security_response/definitions.jsp
Q2 : In the "Clients" view / panel, we never know what is the date of current virus definitions. In 10.x version, it is easy to view the virus definition version in parent and in client so that it is also easy to realize all client get the last version of virus defintion.
As an Administrator, you may check the Graphical Endpoint Protection status on the Home page, and if you see any "out-of-date" clients simply click on it and it would provide you the report with the list of clients.
Whereas, in the clients view panel, change the View to "Protection Technology" and you would see the Virus definitions dates of each component.
Hope that helps!!