The reference to "equiv earth days" was to establish the unit of measure in reference to the inception event at which point earth did not yet exist.
Schroeder explains the concept further by looking at the Hebrew roots of the terms and the Scriptural reference to "evening" and "morning" - namely, that the terms mean from "chaos" to "cosmos." He also underscores the wording of the First Day as compared to Day 3 etc. - namely, that it was the first day, the beginning of time.
>>the first day, the beginning of time.
I like it.
It’s consistent with my view that time is a derivative function of state change that progresses relative to E within the inertial frames in which it’s being observed.