This derivation was introduced in commit
e1d60a05af55daadaeaf85d14869459b9b8c9635 with version 2.2.2 but the
sha256 hash in that commit actually corresponded to version 2.2.1,
as you can see below:
$ nix-prefetch-github --rev "v2.2.1" fitnr convertdate | jq '.sha256'
"1xgi7x9b9kxm0q51bqnmwdm5lp8vwhx5yk4d1b23r37spz9dbhw5"
(cherry picked from commit 3e84c7ea0d3872e660ba0f3a8c2a0971e7df5dd6)