How do I calculate NCOER time?

wherever they left from, that command owes a change of rater from 1 AUG 2020 to 6 NOV 2020.
New assignment started 7 NOV 2020, so rated period starts 7 NOV 2020.
That annual will go 7 NOV 2020 to 6 NOV 2021 with the following dates input for non rated time:
7-24 NOV 2020 code I or Z
17 FEB - 9 APR 2021 Code S

I believe this FAQ might help
What is the NCOER Thru date / How to find NCOER Thru Date?
An NCOER is due when the “Thru” date will be 12 rated months (365 rated days) after the arrival or assignment date while performing the same duties under the same rating officials during this rating period. However, if an event occurs that requires the preparation of an OER or NCOER (for example, “Change of Rater”) before the 12 rated months (365 rated days) have accumulated, an OER or NCOER will be rendered with a “Thru” date that corresponds with the event requiring an evaluation.

If you put the codes in correctly in EES, it will help you calculate the new date that is needed.
This article has been made to offer NCOER help to anyone who needs it.
https://www.soldiersspot.com/post/army-ncoer-faqs-for-the-ncoer-writer