Geezzz...Now I thought Revelation is purely a symbolic book of the Bible. That 7 yr period is a symbolic number.
2Pe 3:8 But, 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.
7 year = 2,520 yrs. 7 x 360=prophetic year
Many think Daniel 9:24-27 (Daniel's 70 weeks - one week = 7 years) pinpoints the 7-year period of Revelation (v.26b-27) as the previous 69 weeks had accurately described Israel's future up to the Lord's crucifixion in v.25-26a.
I think I Peter 3:4-9 is a very brief history of the world to make his point about people saying, "...all things continue as they were from the beginning of creation" (v.4). Again with the Lord's help, check out how the 7 days of creation map to the major defining (Biblical) characteristic of each of the six-thousand-year period since Adam and the next thousand (the Lord's return and rule maps to his day of rest).
As you know, Biblical prophecy is something we need the Holy Spirit to show us since it was inspired by Him. Only the Spirit can "rightly divide the Word of truth." If you ask Him with a sincere heart, the Lord can show as I believe he has me, how perfectly Jesus' discourse on his 2nd coming & end of the world in Matt 24 (& Mark 11, Luke 21) maps with Revelation.