The Kubernetes kubernetes_build_info metric contains label build_date.
Example:
kubernetes_build_info{build_date="2023-10-18T11:33:23Z",compiler="gc",git_commit="07a61d861519c45ef5c89bc22dda289328f29343",git_tree_state="clean",git_version="v1.27.7",go_version="go1.20.10",major="1",minor="27",platform="linux/amd64"} 1
How to convert the build_date label to number of seconds since "now" using MetricsQL?