How Quickly Does It Take for a Body to Decompose?

In January of 1953, there is a grounds keeping team in the park that is clearing brush near this old fish hatchery and they make a grizzly discovery. Underneath several layers of leaves and pine needles is a cheap fur coat which has been degraded to a point where it's almost down to its lining. They don't know if it's children yet or what, but two separate skeletons. And it's been raining. It's been cold, there might have been snow. How quickly does it take for a body to decompose perhaps in cold environments and wet environments like this? It just varies, I guess.