I have non-WSUS Windows 10 Pro machines set to defer feature upgrades for 120 days. So when does the 120-day counter start?
According to this post on the AskWoody forum, “Deferral days are from release date to channel of each version.” By “release date to channel,” the user means the date that the version changed from “Semi-Annual Channel (Targeted)” to “Semi-Annual Channel.” In the case of version 1803, that was on July 10, 2018.
Another user confirmed in a reply on August 28 that “1803 went SAC [Semi-Annual Channel] on 7/10/2018, 49 days ago. With deferrals set to 49 days or less, my VM wants to update to 1803.”
I found a page that will let me add days to a date: https://www.timeanddate.com/date/dateadd.html. Adding 120 to July 10 brings me to November 7:
https://www.timeanddate.com/date/dateadded.html?m1=7&d1=10&y1=2018&type=add&ad=120