Why most of registration are in the same minute od different hours

I find out in one project are most of registration in the same minute. For example 8:09, 9:09, 12:09, 16:09, 19:09, etc. Sometimes is some registration in different minute. Before couple of months it was in minute 08, before 34, etc. It Is quite sophisticated and I accidentally revealed. It looks like work of robot, but name Is normal, e-mails too and IPs responds to cities which user profile contain. In Addition registration Is neccessary to confirm via e-mail.

What IT could be? Is some robot, which do it? What Is the intention?