REST API v2 - Rank change date?

khill- Following details are associated with the user for a rank.

"rank" : {
        "type" : "rank",
        "id" : "27",
        "name" : "Rank Title",
        "position" : 21,
        "bold" : false,
        "color" : "000000",
        "roles_granted" : {
          "query" : "SELECT * FROM roles WHERE ranks_granting.id = '27'"
        },
        "roles_removed" : {
          "query" : "SELECT * FROM roles WHERE ranks_removing.id = '27'"
        },
        "formula_enabled" : false,
        "formula" : "",
        "simple_criteria" : {
          "type" : "simple_rank_criteria",
          "role" : { },
          "user" : { },
          "number_of_posts" : 5,
          "number_of_page_views" : 0,
          "number_of_signins" : 0,
          "minutes_online" : 0,
          "minutes_since_registering" : 5760,
          "simple_formula" : "(posts - deleted_posts >= 5) && (registrationAge >= 5760)"
        }
      }

You can get above information with following query.

select rank from users

There is no field like Rank Date. However, you can get the ranking formula and some other details.

https://community.lithium.com/t5/Developer-Documentation/bd-p/dev-doc-portal?section=commv2&collection=users#fields-rank