This is a site that allows you to see the date you created your account. Simply paste the ID in the empty area and wait for the site to process your ID. The date you joined Discord will appear in the black rectangle under your ID. It will show you the date and time you first joined the community.
The easiest way to report someone on Discord is to simply tell a moderator of the server that the inappropriate behavior occurred in. If you want to report something to Discord’s own Trust & Safety team, you’ll need to turn on the app’s Developer Mode.