diff --git a/src/core/clock.ml b/src/core/clock.ml
index a9282522..473af440 100644
--- a/src/core/clock.ml
+++ b/src/core/clock.ml
@@ -5,13 +5,25 @@ type t = { now: unit -> Timestamp_ns.t } [@@unboxed]
 
 let[@inline] now (self : t) : Timestamp_ns.t = self.now ()
 
-(** Clock using {!Unix.gettimeofday} *)
-let unix : t =
-  { now = (fun () -> Int64.of_float (Unix.gettimeofday () *. 1e9)) }
+open struct
+  module TS = Timestamp_ns
+
+  let ns_in_a_day = Int64.(mul 1_000_000_000L (of_int (24 * 3600)))
+
+  (** Current unix timestamp in nanoseconds *)
+  let[@inline] now_ptime_ () : TS.t =
+    let d, ps = Ptime_clock.now_d_ps () in
+    let d = Int64.(mul (of_int d) ns_in_a_day) in
+    let ns = Int64.(div ps 1_000L) in
+    Int64.(add d ns)
+end
+
+(** Clock that uses ptime. *)
+let ptime_clock : t = { now = now_ptime_ }
 
 module Main = struct
   open struct
-    let main : t Atomic.t = Atomic.make unix
+    let main : t Atomic.t = Atomic.make ptime_clock
   end
 
   let[@inline] get () = Atomic.get main
diff --git a/src/core/dune b/src/core/dune
index 5b1001ea..1c0ae1ab 100644
--- a/src/core/dune
+++ b/src/core/dune
@@ -10,6 +10,7 @@
   (re_export opentelemetry.emitter)
   pbrt
   threads
-  unix
+  ptime
+  ptime.clock.os
   mtime
   hmap))
diff --git a/src/ptime/dune b/src/ptime/dune
deleted file mode 100644
index 8dfe6bd8..00000000
--- a/src/ptime/dune
+++ /dev/null
@@ -1,5 +0,0 @@
-(library
- (name opentelemetry_ptime)
- (public_name opentelemetry.ptime)
- (synopsis "clock for opentelemetry using ptime")
- (libraries opentelemetry.core ptime ptime.clock.os))
diff --git a/src/ptime/opentelemetry_ptime.ml b/src/ptime/opentelemetry_ptime.ml
deleted file mode 100644
index 1862498f..00000000
--- a/src/ptime/opentelemetry_ptime.ml
+++ /dev/null
@@ -1,32 +0,0 @@
-open Opentelemetry_core
-
-open struct
-  module TS = Timestamp_ns
-
-  let ns_in_a_day = Int64.(mul 1_000_000_000L (of_int (24 * 3600)))
-end
-
-(** Current unix timestamp in nanoseconds *)
-let[@inline] now_unix_ns () : TS.t =
-  let span = Ptime_clock.now () |> Ptime.to_span in
-  let d, ps = Ptime.Span.to_d_ps span in
-  let d = Int64.(mul (of_int d) ns_in_a_day) in
-  let ns = Int64.(div ps 1_000L) in
-  Int64.(add d ns)
-
-let clock : Clock.t = { now = now_unix_ns }
-
-(** Nicer pretty-printer *)
-let pp_debug out (self : TS.t) =
-  let d = Int64.(to_int (div self ns_in_a_day)) in
-  let ns = Int64.(rem self ns_in_a_day) in
-  let ps = Int64.(mul ns 1_000L) in
-  match Ptime.Span.of_d_ps (d, ps) with
-  | None -> Format.fprintf out "ts: <%Ld ns>" self
-  | Some span ->
-    (match Ptime.add_span Ptime.epoch span with
-    | None -> Format.fprintf out "ts: <%Ld ns>" self
-    | Some ptime -> Ptime.pp_human () out ptime)
-
-(** Install as main clock. *)
-let set_as_main () = Clock.Main.set clock
diff --git a/src/util/dune b/src/util/dune
index 70a6f758..dcb8951b 100644
--- a/src/util/dune
+++ b/src/util/dune
@@ -4,5 +4,6 @@
  (flags :standard -open Opentelemetry_atomic)
  (libraries
   (re_export opentelemetry.atomic)
+  ptime
   opentelemetry.domain)
  (synopsis "Basic utilities for opentelemetry"))
diff --git a/src/util/timestamp_ns.ml b/src/util/timestamp_ns.ml
index 73e4f3ef..5a8eae63 100644
--- a/src/util/timestamp_ns.ml
+++ b/src/util/timestamp_ns.ml
@@ -5,4 +5,17 @@
 
 type t = int64
 
-let pp_debug out (self : t) = Format.fprintf out "<timestamp: %Ld ns>" self
+open struct
+  let ns_in_a_day = Int64.(mul 1_000_000_000L (of_int (24 * 3600)))
+end
+
+let pp_debug out (self : t) =
+  let d = Int64.(to_int (div self ns_in_a_day)) in
+  let ns = Int64.(rem self ns_in_a_day) in
+  let ps = Int64.(mul ns 1_000L) in
+  match Ptime.Span.of_d_ps (d, ps) with
+  | None -> Format.fprintf out "ts: <%Ld ns>" self
+  | Some span ->
+    (match Ptime.add_span Ptime.epoch span with
+    | None -> Format.fprintf out "ts: <%Ld ns>" self
+    | Some ptime -> Ptime.pp_human () out ptime)