[GrandEagle]

but I have no idea how long a "day" was, as mentioned in Genesis

We can look to Genesis for that answer:
Gen 1:13 "And the evening and the morning were the third day."
God says the same about each day of creation.
Again in Ex 20:
11 For in six days the LORD made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore

Ex 31:17 It is a sign between me and the children of Israel for ever: for in six days the LORD made heaven and earth, and on the seventh day he rested, and was refreshed.

Cordially,
GE

[Luna]

Sorry, but I don't believe in a literal 24 hour period for each day it took God to create the earth. I don't think God's sense of time is the same as ours. But again, I'm not going to worry about it. It really has no bearing on my eternal salvation.