If you have seen his birth certificate, I find it strange that you haven't added his name at birth in his profile. Here is his baptism in the churchbook of Grindheim parish in Bjelland, Vest-Agder, Norway, baptism no. 5: https://www.digitalarkivet.no/kb20060106040667
His first name is Ole. He is born January 10th 1878 (12th is deleted). He is baptized at home February 9th 1878 (which then becomes his date of baptism) by Abraham Iversen Udbostad (the farm he is living on may be named Ubostad today). Ole's baptism is confirmed in the church March 3rd. Ole is born in wedlock. His parents are (translated to English) Farmer Søren Johnsen (born 19/7 1839) and wife Anna Olsdtr. (born 18/5 1844) and they live on the farm Seland. (Seland is an address, not a lastname). Witnesses at Ole's baptism: Rebekka Gundersdtr., Rangdi Simonsdtr., Reier Reiersen, Niels Danielsen, Lars Simonsen Seland. (Since the farmname is written only after the last witness, it means that all of them are living on the farm Seland.
If he was know in the Americas as Olav that would mean he changed his name as an adult, because he is baptized Ole, because his baptism record (and therefore his birth certificate) states that his name was Ole, not Olav.
Thank you for taking the time to write and give me this important information. MyHeritage has the date October 1, 1878. Olav's (or Ole's) oldest brother John wrote Seland-Slekta about 1948. (I have a copy on my computer). In the printing of the book, my father's name (#7) was inadvertently omitted, so the they sent a copy of his birth certificate with the book. Unfortunately, that book got misplaced. If I am wrong on the spelling, it won't be the first time.
Apparently you are in the tree, but I do not see your name. If you wish to get in touch, that can be arranged. I am in Canada.
That dateproblem is a normal mixup because americans stick to writing MMDDYYYY instead of how most of the rest of the world is writing dates DDMMYYYY. So when an american interpret the date 10011878 he sees October First 1878, while the correct date is January Tenth 1878, or as I would have said it Tenth of January 1878.
It would help if the few countries still using this out-of-date way of writing the dates changed to how most of the rest of the world Write dates.