Hi…,
Welcome.
The AIRAC cycle dates are shown at AIRAC Cycle Dates.
We shall consider adding these dates to the AIRAC package in Navigraph Navdata Center which is the basis for the next FMS Data Manager.
In my Calendar, I have AIRAC Release 0900 UTC 15 July 21 and repeating every 28 days.
Generally we publish an hour or two before this.
Cheers
Ian