User Probber has created a realtime analog clock with flowgraph which shows the current time of your PC in Crysis. This is a really good example on how to use the Time:RealTime node in flowgraph and visualize it with an analog clock.
Probber has attached a good example video of how it looks ingame (Windows Media Video | 1.45MB):
Finally you can take a look at the flowgraph for the clock and how to connect the Time:RealTime node with the TimeOfDay feature:
Now it is up to you to implement such a feature into your map to make some things depend at what time the player is playing or just add working clocks into it!
Last but not least a short quote from a forum member who has seen this:
That is AWESOME.
- Forum thread: real time -> time of day (?) + analog clock
-Crymod Staff Team