Venezuela creates its own unique time zone on Sunday, putting the clock back half-an-hour on a permanent basis.
President Hugo Chavez says that an earlier dawn means the performance of the country will improve, as more people will wake up in daylight.
"I don't care if they call me crazy, the new time will go ahead," he said.
But critics say the move is unnecessary and the president simply wants to be in a different time zone from his arch-rival, the United States.
The new time puts Venezuela four-and-a-half hours behind Greenwich Mean Time, and out of step with all its neighbours.
The move had first been announced in August, but it has been delayed twice because international bodies and Venezuela itself were not ready to implement the change.
Science and Technology Minister Hector Nacarro praised the measure.
"I see it as a very positive thing that while there is light we can be in it," he said.