it is possible, mine says "oh no not you again,please log off now"
see how here... Make Windows 7 Welcome you With an Audio Voice Message During Logon
i think this page is the one i used originally. http://mintywhite.com/software-revie...ogin-quicktip/
actually, re reading your original post, i dont think you can get it to speak the time, or be able to specify whether it is morning, noon or night.
perhaps a third party clock that has speech may do that for start up
edit,heres one, it will use microsoft anna so if you can get it to run with the other message then it will all sound like one message. http://www.cinnamonsoftware.com/desktop_clock.htm
as for the greeting of the time of day, i would just have it say hello and your name.
As the clock will say the time then you dont really need the message to say morning or evening