Power Query Concatenate list of dates

Hello,

Can anyone help me in how to concatenate a list of dates, I've tried various options my latest failure is with ; List.Accumulate;

I was hoping that as ; source

= { "a", "b", "c"}

 List.Accumulate( Source, "", (a , b )=> a & " "& b )

gave me a , b , c , I could use it to join a list of dates, but i get the error

 We cannot apply operator & to types Text and Number.

As the ampersand is used when creating an accumulative total using Listaccumulate, eg

a & {List.Last(a) + b }

I wondered if anyone might have some suggestions? Work book included showing concatenated text and failure to work with numbers.

Richard

A workbook will always help, if only to eliminate possible issues. I presume this is to do with PowerQuery? Your thread title needs to be a bit more specific, please.