Could also be "clocks will be changed one hour backwards (throughout the country)", or then "clocks will changed back". But okay just the same, it´s that in this way it adds some detail to the sentence, which could be important. I mean, when speaking about Daylight Saving Time.
Obviuosly, when talking in general ways they use "change the clock", as in this case:http://www.webexhibits.org/daylightsaving/b.html
The title of the heading "When we change our clocks" isn´t specific, it talks generally about the whole of DSTs, the ones from the past and the ones to come.