Aeon as defined by The Incomplete Encyclopedia of The Tellurian Throne of Earth and Mars 541st edition:
Aeon, a galactic season defined as 1/4th of a galactic year (63,000,024 neoclassical Tellurian years).
There is much debate in the least significant digits, some scholars insist tit should be as few as 13 or as many as 67 but the majority find 24 to be adequate. It should be noted some numeric heretics insist on simply dropping the two least significant digits and rounding off to an even 63,000,000. Some scholars point out that the length of the neo-classical Tellurian year is an educated guess that is in conflict with the time-span reported by chrononauts but it has held as the modern definition since the beginning of the as of yet unresolved Andromedan conflict.
At the time of this writing it is currently the 68,415th year of the 78 Aeon. It is what many consider the last Aeon as near the end of this Aeon the tellurian engines will fail and without the energy stabilizing transfer Sol unchecked will resume it's expansion and consume Earth and Mars, even worse, this incident will unchain Thanatos and all the galaxies that could be reached using tri-light drive from the dawn of the 63rd Aeon to approximately 14,000 years post Telluric Apocalypse and the Thanatos Consumption will ( for lack of a better term) be consumed.
Footnote in regard to fleeing the Telluric Apocalypse:
Some have questioned "Why the population of Earth can not be evacuated by time travel" ? This question is of course based in ignorance as transporting even even a tenth of the known sentient population of Earth and Mars would require the consumption of about 13% of the combined mass of the Milkway/Andomeda galaxies; such a monumental project is agreed to simply not be worth the effort.
Footnote to the footnote:
Some engineers of the Reformed Church of Neo-Arhcaic Olympian Trans-h-umanity claim it would be entirely possible to use a significant mass appropriated from an adjacent multiverse to move the population of all suspected sophonts in the core of the Thanatos Consumption Zone to a safe portion of a nearby cosmos. Serious consideration of this endeavor recognizes the need for unprecedented cooperation of many moralities, species, and polities and the reaction of residents in portions of the multiverse with useable mass is unlikely to prove to be favorable. Even the most senior of engineers can't all agree on what constitutes the core of the Thanatos Consumption Zpne (representatives of polities on a defined fringe always seem to insist they are part of the core). Relocation to a nearby cosmos seems to be an unlikely prospect.
It should be noted appoximately 1.3% of the mass of the Milkyway Galaxy was consumed by tri-light drive and other means during The Great Sentient Exodus of the 62nd Aeon. It is also suspected a similar exodus may have happened in the 13th Aeon but one must wonder why they were in such a hurry in that distant age (none of the surviving species evolutionary descendants involved in the earlier exodus can provide an adequate answer if aware of the event at all).