Aion is a stretch of time defined by what fills it, not a fixed unit you could put on a clock.
Aion can mean a lifetime, an era, the present world-order, or time without end. Greek speakers used it for the sweep of history a person or nation lives through, and also for the age still to come after this one. It is less a measurement than a description of a period's character - "this age" carries decay and hostility to God, "the age to come" carries reversal of all that.
Because of this, aion sits at the boundary between history and eternity without settling on either side. Paul can call Satan "the god of this age" and, a few lines later, speak of glory belonging to God "forever and ever" - literally "unto the age of the ages" - using the same word to mean a bounded era and an unbounded one stacked on itself.
and the enemy who sows them is the devil. The harvest is the end of the age, and the harvesters are angels.
The harvest at 'the end of the age' shows aion as a bounded era with a definite close.
in which you used to walk when you conformed to the ways of this world and of the ruler of the power of the air, the spirit who is now at work in the sons of disobedience.
'The course of this age' names the present world-order as a hostile system, not just a time span.
The god of this age has blinded the minds of unbelievers, so they cannot see the light of the gospel of the glory of Christ, who is the image of God.
Satan as 'the god of this age' shows aion describing a ruling order people can be blinded by.
But about the Son He says: “Your throne, O God, endures forever and ever, and justice is the scepter of Your kingdom.
The doubled phrase 'forever and ever' pushes aion toward unending duration, applied to God's throne.
English translators split aion between "age," "world," and "forever," depending on which sense fits, and none of those covers the word's full range. "World" (as in the KJV's "end of the world") makes it sound spatial rather than temporal. "Forever and ever," used for the doubled phrase eis tous aionas ton aionon, is really a Greek way of intensifying duration rather than a separate concept from "age."
A popular argument claims aion only ever means "a limited age," so it can never describe endless punishment or endless life - therefore hell must be temporary. This overreads the word. Aion's range genuinely includes unending duration, especially when doubled or paired with God's own eternity; context, not the word alone, decides how long a given aion runs.
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