DAX access value in another table rules

Hi,

I built a two column table using 'enter data' , two columns two dates, I then used add columns to add a column

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to get year,

But when I tried to use these dates to build a calendar I had to wrap in Min or Max, there was only one so didn't matter,

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My question regards why in the fist example , add column, I could use YEAR directly but in the second I had to use the MIN first,
I don't really know what question I need to be asking in order to find the answer, if anyone has an answer or directions to a post on this
I'd be grateful.

RD

Thank you, on refection that makes perfect sense,
I'd give you a rating but it won't let me,
RD