src/http_info.ml

@@ -60,16 +60,10 @@ let mk_keys ~db_conn (module Keys : Keys.S) ~last_issue_date =
   let zero_limits = [] in
 
   let* denom_l = Keys.denominations () in
-  let denom_l =
-    (* reverse chronological order *)
-    List.sort
-      (fun a b -> Stdlib.compare b.Denomination.stamp_start a.stamp_start)
-      denom_l
-  in
   let list_issue_date =
-    match denom_l with
-    | [] -> Timestamp.zero
-    | dn :: _ -> dn.Denomination.stamp_start
+    List.fold_left
+      (fun acc dn -> Timestamp.max acc dn.Denomination.stamp_start)
+      Timestamp.zero denom_l
   in
   let denom_l =
     (* if `?last_issue_date` query param does not exactly match the `stamp_start`

src/time.ml

@@ -99,6 +99,8 @@ module Timestamp = struct
   let never = uint64_max
   let zero = 0L
   let compare = Int64.unsigned_compare
+  let min a b = if compare a b < 0 then a else b
+  let max a b = if compare a b > 0 then a else b
 
   (* zero if a >= b; never if b=never; otherwise b - a *)
   let diff a b =

src/time.mli

@@ -38,6 +38,8 @@ module Timestamp : sig
   val never : t
   val zero : t
   val compare : t -> t -> int
+  val min : t -> t -> t
+  val max : t -> t -> t
   val diff : t -> t -> Relative.t
   val of_s : int64 -> t