What book in the Bible defines a day in God's time?

Answer 1

"God's time" is "dual."

There is the actual 24-hour day He created through the rotation of the earth in relation to the setting of the sun on the horizon from any fixed point. This is a two-part 24-hour phenomenon: a "nighttime" portion and a "daytime" portion that's defined in the creation account in Genesis 1.

"...God called the light Day, and the darkness He called Night. And the EVENING [night] and the MORNING[day] WERE THE FIRST DAY"! (Gen.1:5)

"...and the EVENING and the MORNING WERE THE SECOND DAY..." (verse 8)

"...and the EVENING and the MORNING WERE THE THIRD DAY..." (verse 13), etc.

God made this time for man, set it in motion, and established a repetitive seven-day period called a "week" whereby man might rest, refresh himself... and "remember creation" and his Creator on the seventh day of this Divinely established week.

Prophetically speaking, however... Peter tells us that God's time is also based on a different "seven-day week"... where each day of that week is a "thousand years" long.

"...beloved, be not ignorant of this one thing, that ONE DAY IS WITH THE LORD AS A THOUSAND YEARS, and A THOUSAND YEARS AS ONE DAY." (II Peter 3:8)

Prophecy speaks of the coming "DAY of the Lord," which will be a THOUSAND YEAR LONG DAY when Christ will rule over the earth from God's Kingdom that He'll establish upon His return in Jerusalem.

This strongly suggests that man has been allotted his own SIX THOUSAND YEAR WEEK to "do his work" and perform the deeds of his life... that will culminate with a thousand year "seventh day" -- the "SABBATH" day -- the "DAY OF THE LORD." When Jesus will cause the earth to rest from its pollution... and command men... to rest from their iniquity.

"For if Jesus [Joshua] had given them rest, then would he not afterward have spoken of another day. THERE REMAINETH THEREFORE A REST [Sabbath] TO THE PEOPLE OF GOD... Let us labour therefore TO ENTER INTO THAT REST [Sabbath]..." (Heb.4:8-11).

God's 24-hour day period of time functions for him in his day-to-day living during his short life span and his generation... ideally, in "the fear of the Lord."

But God's "thousand-year day" period of time functions for Him in working out His plan for the salvation of all of mankind... for all of man's generations.

There's probably much more to say... but, the books of Genesis, Hebrews and II Peter say this much.