I believe the verse you have in mind in speaking of “the fullness of time” is Ephesians 1:10. Let’s read verses 7-10, “In Him (Christ) we have redemption through His blood, the forgiveness of sins, according to the riches of His grace which He made to abound toward us in all wisdom and prudence, having made known to us the mystery of His will, according to His good pleasure which He purposed in Himself, that IN THE DISPENSTATION OF THE FULLNESS OF THE TIMES He might gather together in one all things in Christ, both which are in heaven and which are on earth—in Him” (NKJV).

In this passage the Apostle Paul reminds believers in Christ of 1) the BLESSINGS we currently enjoy because of Christ’s death on the cross (redemption and forgiveness of sins); and 2) the WISDOM and INSIGHT God has given to us so we might know His PURPOSE that will be fulfilled in the coming “dispensation of the fullness of the times.” I believe this phrase speaks of the MILLENNIUM when Christ will return to the earth in power and glory to reign as “King of kings and Lord of lords” for 1,000 years (see Matthew 24:30; 25:31 and Revelation 19:11-16; 20:1-6). God had promised through the Old Testament prophets that this Golden Age of Christ’s reign would come (see, for example, Psalms 2 & 8 along with Isaiah 9:6). They often referred to the Kingdom Age as “the Day of the Lord,” for instead of God allowing mankind to sin and rebel against Him (as they did in former ages), the Lord Jesus Christ will subdue His enemies and all men will be made to bow the knee before Him and own Him as Lord (see again Revelation 19:15-21). This has been God’s purpose all throughout time and thus every “dispensation” (an age where God is dealing in a special way with men) has been leading up to the last and final dispensation, known as the “dispensation of the fullness of the times.”

We saw in Ephesians 1:10 that God will “gather together in one all things in Christ, both which are in heaven and which are on earth.” What does that mean? I believe it means that all saints “in heaven” and saints “which are on earth” will be brought under the Headship of Christ. He will be acknowledged as the Lord of heaven and earth and will receive the worship He deserves. There will be no open rebellion against Christ at that time, even though there will be those born during the Millennium who do not believe on Him for salvation and thus they will only pretend to submit to His authority. Psalm 66 speaks of this, “Say to God, ‘How awesome are Your works! Through the greatness of Your power Your ENEMIES SHALL SUBMIT THEMSELVES TO YOU.’” Again, at this time, all men (even unbelievers) will be made to bow the knee before Christ. We see this revealed in Philippians 2:9-11, “Therefore God also has highly exalted Him and given Him the name which is above every name, that at the name of Jesus every knee should bow, of those IN HEAVEN, and of those ON EARTH, and of those UNDER THE EARTH.”

Regarding the “activities at that time,” it will truly be a time of true PEACE and PROSPERITY where “righteousness will reign” (see Isaiah 32:1 and 65:17-25). As far as Christ “establishing His earthly sanctuary at that time,” there will indeed be a new “Millennial Temple” built where Israel and the nations will worship the Lord (see Ezekiel chapters 40-48).  (378.5)  (DO)