A sprinkler includes a turbine, a nozzle, and a reversing planetary gear drive. The reversing planetary gear drive rotatably couples the turbine and the nozzle through an additional reversing mechanism external to the planetary gear drive. The planetary gear drive includes a shift sun gear capable of axially shifting between raised and lowered positions to alternately drive a non-axially shifting first planet gear that in turn drives a first ring gear and a non-axially shifting second planet gear that in turn drives a second ring gear through an idler gear, the first and second ring gears having different gear tooth profiles to thereby change a direction of rotation of the planetary gear drive and rotate the nozzle in clockwise and counter-clockwise directions at a substantially uniform predetermined speed of rotation.