Just a little background on Satem and Centum......
If you have read anything about the IE language groups you might have run across the terms satem and centum...well here is the quick and dirty.

The original *k sound of PIE is preserved in some IE languages for the most part (except for the Asian IE language, Tocharian) these languages are found in the western IE world, in other words Europe. The latin word for hundred is Centum, OI = cet, Greek = heketon and Gothic = hund. You may note that the *k sound is switched according to Grimms Law into the 'h' sound in the germanic languages. These and other western European languages are in the Centum family.

The Satem family is named after the Irainian word for hundred. The Indic languages, Armenian as well as Baltic and Slavic all fall within the Satem group.

There is no real way to date when the split occurred or why.