Learn Swedish: Avgången är klockan halv fyra. - The departure is at half past three.

Yes, fyra means four! This is a very common trap for English speakers. In Swedish, halv (half) looks forward to the upcoming hour, not the one that just passed. So, halv fyra literally means "halfway to four" (3:30). If you wanted to say "half past four" (4:30), you would say halv fem.

Why isn't there a word for "at" before the time?

In English, we say "at half past three", but in Swedish, the word klockan (the clock) usually does that job for you. You don't need to add a preposition; just saying är klockan halv fyra (is the clock half four) is all you need to state the exact time something happens.

How is the word avgången (the departure) formed?

It is built from the prefix av- (off/away) and the noun en gång (a walk/going, from the verb att gå). Together, en avgång literally means an "off-going" or departure. The -en at the very end is the definite article, turning it into "the" departure.

If I wanted to start the sentence with the time instead, how does the word order change?