How do I remove birthday entries

[jgt1942]

I have a note 8 with Verizon, previously I had Sprint. Somewhere along the line a bunch of birthdays got added to my calendar. I use Outlook on my PC and I have a few contacts where I have entered their birthdays and these are the only birthday entries I want on my phone. When I open the calendar on my phone and see several birthday entries for a contacts where I do NOT have the contact in Outlook (Outlook is synced with my phone via Akrutosync, I only sync contacts, calendar, task, I do not sync my emails).

1. How do I determine where the birthday entries that I don't want came from?
2. How do I stop them from getting in the calendar on my phone?
3. How do I remove the entry in the calendar?

On the phone I'm using the calendar that was made available by Sprint/Verizon, I've never used another calendar on the phone.

I was able to delete a few of the birthday entries by a long click on the entry and selecting delete but for most this is not an option.

Where I do have a birthday in Outlook 2013 on my Win10 PC I do want those in my calendar on the phone and my PC.
Thanks