use ptime library to get rfc3339 timestamps w/ timezone

lib/logging/dune

@@ -1,4 +1,4 @@
 (library
  (package talircd)
  (name logging)
- (libraries unix))
+ (libraries ptime ptime.clock.os))

lib/logging/logging.ml

@@ -7,8 +7,18 @@ type level =
 
 external int_of_level : level -> int = "%identity"
 
+module Time = struct
+  (* TODO: abstract this? *)
+  type t = Ptime.t
+  let stamp = Ptime_clock.now
+  let pp = Ptime.pp_rfc3339 ()
+             ?tz_offset_s:(Ptime_clock.current_tz_offset_s ())
+  let to_string x =
+    Format.asprintf "%a" pp x
+end
+
 type writer =
-  ts:float ->
+  ts:Time.t ->
   ns:string ->
   lvl:level ->
   string ->
@@ -53,7 +63,7 @@ type 'a log_function =
   ((('a, Format.formatter, unit) format -> 'a) -> unit) -> unit
 
 let write logger lvl msg =
-  let ts = Unix.gettimeofday () in
+  let ts = Time.stamp () in
   let ns = logger.namespace in
   Option.iter (fun w -> w ~ts ~ns ~lvl msg) logger.writers
 
@@ -147,11 +157,7 @@ module Pretty = struct
   let ansi_off  = "\x1b[0m"
 
   let pr_timestamp bp ts =
-    let ts_ms = int_of_float (ts *. 1000.0) mod 1000 in
-    let tm = Unix.localtime ts in
-    Printf.bprintf bp "%04d-%02d-%02d %02d:%02d:%02d.%03d"
-      (tm.tm_year + 1900) (tm.tm_mon + 1) tm.tm_mday
-      tm.tm_hour tm.tm_min tm.tm_sec ts_ms
+    Buffer.add_string bp (Time.to_string ts)
 
   let pr_spaces bp n =
     for _ = 1 to n do