Posted Jan 27 2013 - 09:06 AM
It seems to me that those who use the expression refer to the time they consider to be "before" the current era. The exact definition can vary.
On Mata Nui, the Turaga seemed to mean pre-Cataclysm. The Bahrag appeared to use this as the baseline as well, since the "before-time" of the island would be when it was still barren, and it was only created right after the Great Cataclysm in the first place. Within the Toa Metru's stories, however, "Time Before Time" is even further back, either back to the point where none of them even existed (as per their telling of the Great Beings) or at least as far back as anyone can remember (Keetongu's disappearance, in one case).
It'd be interesting to know if this particular expression stems from the Great Beings, if they used similar terms to describe their "eras".