Membership status changing from Grace to Expired a day later than expected
The 'Fixed Period Rollover Date' relates to the start of memberships and is not relevant here.
This is about date maths ...
Grace is defined as End Date (Dec 31) to End Date + 6 months. So what date is &quot;6 months&quot; after Dec 31?  If you increment the month and leave the day of month fixed, you get &quot;June 31&quot;.  That doesn't exist, but if we think of &quot;June 31&quot; as the day after June 30, you get to the last day of Grace being July 1 (not June 30).
So then changing to Expired on July 2 makes sense.
Intuitively we think of Dec 31 as 'end of December', and so 6 months later is 'end of June' - but that's not how it is calculated.
See Example #3