I wasnt able to find a whole lot of discussions on different date format.
Is there a built in function that can read date format by locale setting?
There are dates that are formatted like
"YYYY-MM-DD", "DD-MM-YYYY" and it seems like these with "-" aren't liked by
parseFunction.

Would I just have to figure out what locale system setting is and try to
figure out the format to parse it in the "/" format?

var formatterateFormatter = new DateFormatter();
formatter.formatString = "MM/DD/YYYY";
dateinString = formatter.format("2008-7-10");

This seem to work great.
But what happens with locale settings where it's DD-MM-YYYY
will it recognize if it is 10-12-2008 (will it know it's 10 for day and 12 for
month?)

just curious

If I am not mistaken, when you develop your app you need to know the format of
any data that will be accessed, and then brought into the application UI.

Then in your UI code you can use the formatters to format the data based on
the current locale.

If you cannot reliably know the meaning of the data accessed by the app
"MM/DD/YYYY" or "DD/MM/YYYY", then you cannot hope to reliably display it
accurately in various locales in the UI.