ancient times; prehistoric times; the distant past; a very long time ago
Refers to a time far in the past, often with a sense of great antiquity. Can be used as a noun or adverbially.
In ancient times, this area was apparently under the sea.
That's a story from the distant past.
This festival has been held in the village since ancient times.
A fossil from ancient times was found in this rock layer.
They say that long, long ago, this area was under the sea.