Strange calculated age result

[emyoulation]

The following thread has a more extensive discussion:

Date quality vs. modifier

I am re-reading carefully the user manual and simultaneously study the source code. I am puzzled by an apparent ambiguity in dates. A modifier is “about” which implies some uncertainty about the date. Quality could (should?) then be set to “estimated”. Isn’t there redundancy between modifier and quality? Is a date with no modifier but with quality “estimated” equivalent to an “about” date? How is this related to the “precision” of about, before and after dates when comparing? Would it make se…