>> I tried to add these non-working days to the custom calendar but I’m not able to change that. I can’t change task calendars because we don’t want any tasks being done during these time periods.
What you mean by the above is not clear to me.
>> Is there a way to add these non-working days to my project calendar without altering every individual resource calendar?
What is the point on adding non-working days to the project calendar but not getting the changes reflected on the resource calendars ?
Task calendars are usually created as a copy of the project calendar. Resource calendars are created based on the project calendar by default.
