Holocene epoch
Geological term for the current epoch, beginning after the last Ice Age.
完新世は約1万年前に始まった。
The Holocene epoch began about 10,000 years ago.
完新世 is the standard geological term for the Holocene epoch, whereas 現世（げんせい）is a less common variant used in the same sense.
From 完 (complete) + 新 (new) + 世 (epoch), a calque of 'Holocene' (from Greek 'holos' whole + 'kainos' new).