The OYC (Omniversal Year Calendar) is a calendar used for majority of this Realm.
On the Omniverse article, it is explained how The Box's layers collapsed on themselves. These collapses were periodical, and every single one of them took exactly the same amount of time. This amount of time was then measured precisely and labeled as the OYC.
1 OYC is approximately (in Earth measurements) 790 years, 9 months and 29 days. This can be pretty accurately approximated as years.
An OYC has many subdivisions, infact, an OYC has so many nested subdivisions, that the last official one is comparable to a planck time. Contrary to what one might think upon reading this for the first time, every single one of these divisions are used just as much as all of the ones above and below it.
Some divisions are used more and some aren't, there are many types for specific fields and large enough civilizations. The OD (Omniversal Day - a translation only used by humans), is equal to 1/5040th of an OYC, which is equal to around 57 and 1/4 days, about 2 months.
It is currently the year 11,363 OYC and 1,117 OD, and the first Realm was created OYC ago (which means that in 2 OYC, this number will be prime. Prime ages are celebrated much more than regular OYCs).