You can globally add attributes to a large number of constituents at once; however, there is no option to globally add or change the comment start date. It would be very helpful to be able to do this, so we could see older comments vs newer comments. As we often assign 1,000-2,000 at a time, we don't want to edit them one by one.
T. Rash
This absolutely needs to be a thing - it is just common sense!