During which division of geologic time did the most recent ice age occur?
The Quaternary Period
The most recent ice age happened during the period of time known as the Quaternary. This period spanned from 2.6 million years ago to the present. The Last Glacial Maximum was around 26,000 years ago - the time when global ice sheets reached their greatest extent.
As implied, this was only the most recent ice age. The Quaternary ice ages are cyclical and are still cycling. We are currently in an interglacial period, halfway between ice ages. More will probably occur in the future.