Jo Anne continued:
<<I have info from the 1900 Hawaiian census that shows a Manuel
Mello, B/D 1868 in Portugal immigrated to HI in 1887! married to Mary
in 1889 - now do I take that as gospel? ... Dates seem to float up and down. Geez when they interviewed
these people don't they know their own birthdate? Why do they keep
changing, if, in fact, they are the same people?>>
The only thing you can take as gospel is a primary source. A primary source is something that was issued at the time of the event. A birth certificate is a primary source for a birth. A death certificate is a primary source for the death. You can take the birth date off of the death certificate, but that fact is a secondary source. Secondary sources are something that was issued AFTER the time of the event.
Most of our ancestors were illiterate. They did not celebrate birthdays like we do now with a cake and whatnot. They weren't asked for their birthdate like we are when we fill out credit applications, banking forms, Dept of Motor Vehicle stuff, employment applications, etc. And some of our ancestors used their baptism date as their birth date instead.
When I started doing genealogy 21 years ago, I initially signed up for a basic genealogy class at my local adult school. One of the things we were taught was:
1) Who said it?
2) When did they say it?
3) How did they know?
Take a look at this 1880 census (if you have a subscription to Ancestry): goo.gl/9jNb7
If you are researching the John Bedford family (lines 9-15) in the 1880 census, you will know the answer to question 2 above. It was stated in 1880. But if you know that the husband and wife are about 15 years apart in age, and their kids are William, ELIZABETH, Annie, LOLA, and Joseph, you will be completely baffled that the census shows the husband and wife as only 5 years apart and that their kids are William, MARY, Annie, LOUISA, and Joseph. And the kids' ages are way off. Scroll way over to the right. The answer to question number 1 is there. I lucked out on that! (for those without a subscription to Ancestry, it says "Obtained from a neighbor. Could learn no more." And then you look at all their neighbors (for those who can't view it, many are from Portugal, China, Russia, and Canada). I therefore have my answer to question 3: They neighbors really didn't know. They took their best guess.
You'll have to collect every piece of paper you can find on your ancestors. Hawaii is tougher because you are dealing with a U.S. territory and a kingdom. So things are a little different with Hawaiian research. And if you can't find stuff on the husband, chase the wife around. And ALL their kids. Not just your ancestor. The information you need may be on a different kids' record.