How do I delete an entry in my calendar that keeps reappearing?

There is an entry in my calendar that keeps reappearing. If I delete it, it will remain gone for that session. The next time I log into Yahoo or refresh Yahoo Mail, however, it will show up again on the calendar, as if I had never deleted it. Two additional pieces of information: 1. The entry only keeps reappearing when viewed through the calendar within Yahoo Mail. If I access the calendar outside of Yahoo Mail (at calendar.yahoo.com), the entry is always deleted and never reappears. It is only when viewing within Yahoo Mail that it keeps reappearing. 2. If I click on the event, in the box that pops up with options to Edit, Print, or Delete, there is a circle with a line through it in the section where you would see the repeating information (such as when an entry says Repeats Yearly). Further, if you hold your mouse over the circle with the line through it, the pop-up says "This is a recurring event". In previous versions of Yahoo Mail when I experienced this issue, I could just change the calendar view to List, delete the item from there, and it would be gone for good. I know an easy workaround would just be to edit the entry so that it is moved to a date far into the future and just forget about it. I'd rather just permanently delete the entry, though. I also can't understand why the standalone version of calendar (calendar.yahoo.com) is perfectly fine, with the entry permanently deleted, but the same calendar viewed through Yahoo Mail has the entry reappear every time I refresh Mail or sign back in. Thanks for any insight or solution you can provide!