Q:

No reputation changes on this day means

In my reputation tab of my profile page there are a lot of dates with zero reputation changes.
But, some of them showing the message,

We are not showing reputation changes for all dates. If the system shows there is zero rep change means there should be something happened like below,

I need to clarify or get a support from the community that why most of the users got this message several times.
I think this post is not the dup of this, which had a feature request to show any reason for zero rep change. I need the reason for showing There were no net reputation changes on this day.

A:

That usually seems to appear when a vote happened, but was undone again within a grace period. Then in the end no votes are registered, but instead that message appears. 

