You don't own the copyright from anything that you've taken as "references from many sources."
You'll need to check under what kind of copyright those sources are. You'll need copyright clearance and/or source attribution (eg, if those materials are under a Creative Commons licence).
For some values, there's a defined length or maximum length. Like US Zip Codes are 5 digits, or 10 digits if you allow for zip-plus-4 and they hyphen. Credit card numbers are typically 16 digits. Etc.
Of course many values aren't controlled by some central authority and don't have defined lengths. A person's name would be an obvious example. In these cases, ...
For a date, it's pretty easy once you have chosen the format.
The format YYYY/MM/DD requires a minimum of 10 characters.
For things like name and surnames, you should consider the longest surname and name your country has. If it is international, just put it up to 32 characters as most websites do.