Hi @Tim_Richardson,
Let me know if I’m getting closer (doc is public, so everyone can access to it).
Basically, you’re asking a duration in years, months and days that I have roughly constructed.
I didn’t check if this is a topic already asked: let me browse a bit.
Anyway: am I getting closer?
[edit]: Yep, apparently it’s still an open topic: More Duration Options (Especially Years/Months)