God is Eternity
Everything that God is/does is One Divine Eternal Act. God is Timeless and Placeless. God is everywhere at once and He is beyond Place. God is everywhen at once and He is beyond Time. God is within Time and beyond Time. God is within Place and beyond Place.
It is not correct to say that God knows an event before it happens, or that He remembers an event after it happens. God is beyond Time. God knows all events, throughout all Time and beyond Time, all in the One Divine Eternal Act that is God. His knowledge of events is Eternal, unbounded by Time. His knowledge of the past is not a mere memory, and His knowledge of the future is not mere foreknowledge. The Act of God knowing past, present, future is exactly the same as the Act of God existing, willing, loving, and so on. And all the acts of God are One Act. For God Himself is that One Divine Eternal Act and nothing else.
Eternity is God and not merely a quality of God. Only God is Eternal. Eternity means that God is uncreated. Eternity means that God is before, beyond, and within all created things. Eternity means that God is everywhere, and is before and beyond Place, and that God is everywhen, and is before and beyond Time. God does not literally “dwell in Eternity,” for Eternity is God. God cannot be contained within anything. God alone is Eternal.
To be truly and completely Eternal is to exist always, with no beginning and no end. Every created thing has its creation as its beginning. Therefore, no created thing is truly and completely Eternal. God alone is Eternal. God is Eternity.
Heaven is with God
Heaven is not divided into different times or different places. Heaven is not divided into different moments, seconds, minutes, hours, days, weeks, months, and years. Heaven is not divided into different houses, streets, cities, states, countries, continents, planets, galaxies, etc. Heaven is timeless and placeless.
When someone travels, they start at one place and time, they move through different places at different times, and they arrive at another place at a later time. Heaven is not like travel. You cannot travel in Heaven, because Heaven is timeless and placeless. Events in Heaven are not ordered according to when and where. Heaven is like all Time put together at once, or like no Time at all. Heaven is like all Place put together at once, or like no Place at all. Heaven is beyond Time and beyond Place. Heaven is both timeless and placeless. Heaven does not refer merely to timelessness, or timefullness, but also to placelessness, or placefullness.
Heaven is beyond Time and Place. Heaven is not a place in the material universe. Heaven is not closer to one city, and farther from another city. There is no set of directions by which one can travel to Heaven as a location. Heaven is just as close to, and just as far away from, one city as another, one planet as another, one galaxy as another. If you die in one city, your journey to Heaven is no shorter, nor any longer, than if you died in another city, or another country, or any other place in the universe. Heaven is no place within the universe. If Heaven were a place in the material universe, then it would be closer to one city and farther from another, and it would have a location that could be specified by a map and a set of directions.
Heaven contains created things, such as the Angels, the souls of the Elect, the body and soul of Jesus Christ, and the body and soul of the Virgin Mary. Heaven was created by God as a type of container for certain created things. Heaven is like all Place put together at once, or like no Place at all. Heaven could be called placeless, or even place-full. Yet Heaven is outside of Place and beyond Place. Heaven is for the Blessed who dwell with God, Who is Eternity. To be with God is to be beyond Time and Place.
Heaven is not within Time. Heaven is with God, Who is Eternity. For the souls in Heaven, Time does not pass as on earth, hour after hour, day after day, year after year. Heaven is outside of Time and beyond Time. Heaven is timeless, but not Eternal, for Heaven has a beginning and the first Heaven has an end (Rev 21:1). Heaven is sometimes called eternity, because Heaven is with God, Who is Eternity. But, strictly speaking, Heaven is not Eternity, because Heaven has not always existed.
If you die today, and your spouse dies ten years later, you do not arrive in Heaven ten years before your spouse. You are not waiting in Heaven for ten years to pass, until your spouse dies and joins you in Heaven, because Heaven is outside of Time and beyond all Time. If you die today and your spouse dies ten years later, and if you both end up in Heaven, neither really arrives before the other.
Time and Death
Within Time, there is an absolute order to the occurrence of events. One event occurs before and another event occurs after. From the point of view of someone within Time, your spouse dies ten years after you died. But from the point of view of Heaven, you have both always been there, since Heaven began until this Heaven ends. You enter into the Timelessness of Heaven from a particular point in Time. Your spouse enters into the Timelessness of Heaven from another particular point in Time. But once you are within Heaven, you dwell in the Timelessness between the beginning of this Heaven and its end. Even so, the Blessed in Heaven, and Heaven itself, are not Eternal as God is Eternal. Heaven and the Blessed in Heaven have not always existed. However, within the boundaries of Heaven (its beginning and its end), the Blessed in Heaven dwell in Timelessness with God, Who is Eternity.
Since Heaven is beyond Time and unbounded by Time, within Heaven there is no absolute before and after. When you die, your friend welcomes you into Heaven. And when your friend dies, you are there to welcome your friend into Heaven, regardless of who died when. There is no fixed order of events within Heaven, for if there were, then Heaven would be within Time and limited by Time. On the contrary, those who are in Heaven are with God, Who is Eternity. Thus, Heaven takes on much the same aspect as Eternity. God is beyond all Time and unbounded by Time. God is Eternal. Therefore, those who dwell in Heaven are not within Time, but are with the Eternal God.
A child dies today, but her parents die many years later. When that child arrives in Heaven, her parents are already there to greet her. She does not have to wait and wait, as time passes, for her parents and other loved ones to finally join her in Heaven. There is no waiting in the Timelessness of Heaven. From the point of view of one bounded by Time, it seems as if one person arrives in Heaven before another. But from the point of view of Heaven, everyone who ever will arrive in this Heaven is already there. When a person goes to Heaven, they leave Time and all of its constraints. Heaven is ever present tense.
Christ and Mary
Once Christ entered into Heaven, He has always been there, since Heaven began. Heaven was created before and beyond Time. Even from the beginning of the creation of the universe, Christ was present in Heaven in His Human Nature as well as His Divine Nature. When Adam and Eve were created, Christ was present in Heaven, body and soul and Divinity. When Moses parted the Red Sea, Christ was already present in Heaven, even in His Human Nature. When the Immaculate Virgin was conceived, Christ’s body and soul and Divinity were already in Heaven. When Christ walked this earth and taught and healed, He was also present in body and soul and Divinity in Heaven, beyond Time and Place. (The infinite power of God is able to cause body and soul to be present in more than one place at the same time. Thus, Christ is present in all the hosts of all the tabernacles of the world at the same time. Then, too, Heaven is beyond place.)
Once Mary entered into Heaven, she has always been there, since Heaven began. From Heaven in Eternity, with God who is Eternity, the Blessed Virgin Mary is able to dispense grace to all persons throughout all of Time and Place. She is able to be the Mediatrix of all graces (except those to herself and Christ) because she is beyond Time. If Heaven were not beyond time, then she could only dispense grace from the time that she entered Heaven, and then she would not be the Mediatrix of all graces.
From Heaven in Eternity with God, Mary dispensed grace to Adam and Eve, to the Patriarchs, to her own parents and ancestors. From Heaven in Eternity with God, Mary is Queen over all Creation (except Christ) and has been so since Creation began. When the angels were first created, Mary dispensed grace to them from Heaven, which is beyond Time. Only if Heaven is beyond Time can Mary be the Mediatrix of grace to all angels and all human persons (except Christ and herself). Mary is not the Mediatrix of the graces that the human nature of Christ receives from the Divine Nature within the hypostatic union. Mary is not the Mediatrix of the graces that she herself receives from Christ (in that case, she is the recipient). But of all other graces to Creation, Mary is the Mediatrix. But this is only possible because she is Queen of Heaven, which is beyond Time, with the Eternal God.