In older versions of Windows, you could see the time and date in the system tray on the taskbar. You can still do that in the Desktop mode of Windows 8. But, when you are in the Start screen of Windows 8, this information is missing. The tile of the Calendar application show the date, but what about the time?
If you bring up the Charms Bar, which appears on the right, the current date and time is also displayed in a box on the bottom left corner. The easiest way to bring up the Charms Bar is to use the keyboard shortcut Win + C.
Once I learnt about this, I felt that this was more convenient than a date-time display that is omnipresent on the Start screen. This is less distracting.