Cas is the word for time in Czech.  The units of time are hodina - an hour, minuta, a minute, and vterina for a second, or sekunda, which you may find easier to say.  The word for clock is hodiny, literally translated as "hours" and a wristwatch is hodinky or "small hours".  Be careful - both words are plurals.

There are several types of clocks - slunecni hodiny, that's a sundial, presypaci hodiny - an hourglass or kukackove hodiny a cuckoo clock.

If you come across the expression hodinky s vodotryskem, remember it's not a special type of wristwatch with a fountain attached to it, as the literal translation suggests.  It stands for something unattainable yet useless and people use the expression when someone wants something special which is not to be had ans without really knowing what it is.

It is well known to students of Czech that the language has a complicated system of telling time.  Czechs use quarters, halves, and three quarters and various words change their endings depending on the grammar. To say 'It's twenty to four' in Czech is quite difficult.  

"It's five minutes before forty-five minutes after three, is that correct?  Which by the time you say that it's really ten to four, isn't it.  It means you're always ten minutes late to whatever you're going to.

Well, it's twenty to four in Czech is "Je za pet minut tri ctvrte na ctyri, literally meaning "It's five minutes to three quarters to four".Encouraging, isn't it?

I have one useful tip for you if you don't feel up to penetrating the mysterious system of time-telling in Czech: you can always give digital time and instead of asking people for time, grab their arms and check their watches.  Or one even simpler tip: carry your own watch.

-Pavla Horakova
Radio Prague