Thousand years (dominion): Revelation 20;   Book of Revelation

One day like a thousand years

Ps. 90:4 "For a thousand years in Your sight are like yesterday when it passes by, or as a watch in the night."; 2 Peter 3:7-8 "But by His word the present heavens and earth are being reserved for fire, kept for the day of judgment and destruction of lawless men.  But do not let this one fact escape your notice, beloved, that with YHWH one day is like a thousand years, and a thousand years like one day."
One day (Day of judgment) is given to the repentant hearts where His Word of Life (Yahushua our Messiah) sits on His throne in the temple (sanctified heart of His chosen ones) judging (consuming by His purging fire) the works of opposition that must be separated into the opposing kingdoms at the ends of fleshly ages as to preserve the valuation of good works examined in His Kingdom of Life and to remove the valuation of evil works in the kingdom of death (lake of fire).  Our fleshly temple (present earth) and spirits of mortality (present heavens) are destroyed for His Temple of holiness (new earth) come to our repentant hearts where His Spirit of Life (new heaven) dwells in. 2 Cor. 5:16-19 "Therefore from now on we recognize no one according to the flesh; even though we have known haMashiyach according to the flesh, yet now we know Him in this way no longer.  Therefore if anyone is in haMashiyach, he is a new creature; the old things passed away; behold, new things have come.  Now all these things are from Elohim, who reconciled us to Himself through haMashiyach and gave us the ministry of reconciliation, namely, that Elohim was in haMashiyach reconciling the world to Himself, not counting their trespasses against them, and He has committed to us the word of reconciliation."  The old things passed away are the (earthly) things of mortality subjected to Satan, and the new things come to the repentant ones are the (spiritual) things of immortality subjected to YHWH.  The fleshly minded only look at the outward (literal) things and the spiritual minded only look at the inward (spiritual/figurative) things.

Day of judgment/salvation comes to us 
in His dominion/eternity of Light (1000 years)

The Day of judgment (salvation) comes to us, the spiritual minded, that His love separates us from our old fear (lawless punishment).  We were the children of unrighteousness (darkness) but upon our repentance, we become the children of Day (Light) dwelling in His pure love.  
Matt. 12:36-37 "But I tell you that every careless word that people speak, they shall give an accounting for it in the day of judgment.  For by your words you will be justified, and by your words you will be condemned."; 2 Peter 2:9 "YHWH knows how to rescue the holy from temptation, and to keep the unrighteous under punishment for the day of judgment"; 1 John 4:17-18 "By this, love is perfected with us, so that we may have confidence in the day of judgment; because as He is, so also are we in this world.  There is no fear in love; but perfect love casts out fear, because fear involves punishment, and the one who fears is not perfected in love."; John 3:19-21 "This is the judgment, that the Light has come into the world, and men loved the darkness rather than the Light, for their deeds were evil.  For everyone who does evil hates the Light, and does not come to the Light for fear that his deeds will be exposed.  But he who practices the truth comes to the Light, so that his deeds may be manifested as having been wrought in Elohim."  The Day of judgment is not the future event, but it is now in this world of mortality for all who repent out of the darkness to see His things of Light.  John 12: 31-32 "Now judgment is upon this world; now the ruler of this world will be cast out.  And I, if I am lifted up from the earth, will draw all men to Myself."  We are justified by our wise words and condemned by our foolish words daily.  Without the Day of judgment, we do not know the difference between the words of wisdom and the words of foolishness.

Thousand years (His dominion/perfection/eternity)

The thousand years is indicated in a spiritual sense as the dominance/perfection of all the examination of our obedience to His Law of Life that is separated from the works of impurity that are removed at the day of judgment when coming to repent from the kingdom of mortality.  The longevity in the book of Genesis for those who died before a thousand years (Adam - 930 years old) is understood of their shortage of perfection because of the violation of His Law of Life.  Rom 3:23-24 "for all have sinned and fall short of the glory of Elohim, being justified as a gift by His grace through the redemption which is in haMashiyach Yahushua."  It is the spiritual perception of being perfect as dwelling in His unending Kingdom (glory of our El) for all the true believers.  All the mortals must repent on the day of His judgment to dwell in His Kingdom of eternity (thousand years/dominance).  To reign with our Messiah for a thousand years (Rev. 20:6) is the eternal dwelling in His Kingdom of Life while in the trials of our spiritual lives on the earth, where Satan the father of mortality must be released from the mortal heart (earth) at the time of fleshly expiration as to return our perishable body to the ground (dust) before our imperishable body is brought back to His eternal Kingdom (1 Cor. 15:42-44).

His Day of salvation is the point of reversal from our former kingdoms of mortality/darkness subjected to Satan's dominion/imperfect powers (1000 years) that is multiplied to his words of lawlessness in the mortal heart, to His Kingdom of immortality/Light subjected to YHWH's dominion/perfection (1000 years) that is multiplied to His Word of purity in the repentant/sanctified heart.  1000 means three-dimensional 10x10x10 perfection (YHWH, Son/Word of Life, and Spirit of Life). The ends of our fleshly ages (death) is the short time permitted for Satan to remove our perishable bodies as to return dust to the earth then our imperishable bodies are returned to YHWH, like the wheat and tares grow together till the harvest time, and tares are removed first and thrown at the lake of fire then wheat is preserved to His barn (Kingdom of Life).

Your spiritual life begins with His dominion/perfection (1000) of Light by repentance out of the dominion of darkness dominated by Satan, and multiplies you in the knowledge of YHWH thru His Messianic teachings (New covenant) by His chosen 12 apostles to restore back to the 12 tribes of YisraEl (Body of Mashiyach/Messiah) fully.  2 Peter 1:2-4 "Grace and peace be multiplied to you in the knowledge of Elohim and of Yahushua our Adoneynu; seeing that His divine power has granted to us everything pertaining to life and holiness, through the true knowledge of Him who called us by His own glory and excellence.  For by these He has granted us His precious and magnificent promises, so that by them you may become partakers of the divine nature, having escaped the corruption that is in the world by lust." 

We, the repentant ones, have come to the Day of salvation/judgment upon our repentance, Satan the ruler of this world is put under our feet, for we serve Yahushua the master of Light, and we are judged by YHWH according to our renewing of our minds and hearts doing our deeds daily whether it is His Law of Life or not.  John 12:31-32 "Now judgment is upon this world; now the ruler of this world will be cast out.  And I, if I am lifted up from the earth, will draw all men to Myself.", 1 Cor. 11:31-32 “But if we judged ourselves rightly, we would not be judged.  But when we are judged, we are disciplined by YHWH so that we will not be condemned along with the world.”  All men are drawn to Himself at the ends of their fleshly ages (His harvest times) once both their deeds are separated into the opposing bodies/kingdoms.

All children of eternal Light (Day) separated 
from the eternal darkness (night)

Acts 26:16-18 …to open their eyes so that they may turn from darkness to Light and from the dominion of Satan to Elohim, that they may receive forgiveness of sins and an inheritance among those who have been sanctified by faith in Me.”; 1 Th. 5:5 "for you are all sons of light and sons of day. We are not of night nor of darkness."; Matt. 6:22-23 "The eye is the lamp of the body; so then if your eye is clear, your whole body will be full of light.  But if your eye is bad, your whole body will be full of darkness. If then the light that is in you is darkness, how great is the darkness!"; 1 John 1:6-7 "If we say that we have fellowship with Him and yet walk in the darkness, we lie and do not practice the truth; but if we walk in the Light as He Himself is in the Light, we have fellowship with one another, and the blood of Yahushua His Son cleanses us from all sin."
Upon our repentance, we turn from the dominion of darkness/lawlessness to His dominion of Light at the Day of salvation (judgment) as we become His servants of righteousness/freedom.  The thousand years is not literal, but is figurative as His dominion of Light in the eyes of the spiritual minded.  As we are the children of Light (day) separating from the darkness (night), it is eternal Day (Light) with us (Yahushua says I am the Light, I am in them, they are in Me).
"One day like a thousand years" is to open the door (He is the Door of Light) out of darkness to His Kingdom of eternal Light.  All the mortal things in this world of mortality can be measured and the times/days can be literal counted in this world of mortality, but all the immortal things cannot be measured nor counted as many claim the thousand days in Revelation 20 as the millennium.  Remember that YHWH only sees what is inward (spiritual), not what is outward (literal), and only the spiritual minded can perceive what it means figuratively when seeing its spiritual sense.

Thousand years (dominion): Revelation 20;   Book of Revelation