do u mean on the toolbar or the dock? idk if u can put the time in the dock, but to put the full date on the toolbar:
1. go to the system preferences pane
2. click international
3. click formats
4. in the section that says dates, click customize
5. on the drop down menu where it says "show", find "full" and select it
6. highlight the date that shows up, "friday, january 5, 2007" or watever it says
7. copy it
8. click ok
9. once ur back to the international/formats pane, go to the section that says times and click customize
10. select medium from the drop down menu (it wont work right if its not set to medium)
11. paste the date u copied before the time and put a space in between the two so that it doesnt show up right next to each other...
(if the date shows up as something like - "Sun Sunday, September 23, 2007"
12. go back to the preferences pane
13. click on "date and time"
14. go to the "clock" tab
15. unselect "show the day of the week"