Getting all values of particular custom field

Is it possible to fetch a list of the all the value for a particular custom field used in blog posts?

I’m thinking of, for example having a sidebar menu that would display a list of all the values for a ‘date’ custom field assigned to blog posts, in the same way that a categories menu would, with each date in the list giving access to a page displaying all the items from that year.

I don’t want to use the builtin Archive functions, because the date of a piece of work (I’m working on a showcase site) wouldn’t necessarily correspond to the date the post was uploaded.

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