We received alerts about new pwned discoveries but we cannot see what is new compared to the previous alert.

Adding a date when it has been discovered by hibp will help to focus on new issues and not those already fixed...

It would be better if the spreadsheet with the leak records had a "leak date" column.

A date column would be great, because then all I would nee to do is run a pivot table to see what's new or a graph to should a timeline and how well my message is getting through internally.

Agreed! Often I want to know if the password I changed a year ago is pwned, not one from five years ago, like LinkedIn. It's a parallel service, "WhenHaveIBeenPwned?"

I would vote for 2 date columns: one for date of breach, one for date breach was discovered/made public.