diff --git a/CHANGES.md b/CHANGES.md
index 2577a57e443..f8f84193c47 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -6,6 +6,11 @@
   - Change behavior of `Irmin.Conf.key` to disallow duplicate key names by
     default. Add `allow_duplicate` optional argument to override. (@metanivek,
     #2252)
+    
+### Changed
+
+- **irmin**
+  - Lower bounds for `mtime` is now `2.0.0` (@patricoferris, #2166)
 
 ### Fixed
 
diff --git a/bench/irmin-pack/bench_common.ml b/bench/irmin-pack/bench_common.ml
index 7ba4b5dcbe6..c2c01d11cb0 100644
--- a/bench/irmin-pack/bench_common.ml
+++ b/bench/irmin-pack/bench_common.ml
@@ -17,7 +17,7 @@
 open Irmin.Export_for_backends
 
 let c0 = Mtime_clock.counter ()
-let now_us () = Mtime_clock.count c0 |> Mtime.Span.to_us
+let now_us () = Mtime.span_to_us (Mtime_clock.count c0)
 let last = ref (now_us ())
 
 let dt_us () =
diff --git a/bench/irmin-pack/dune b/bench/irmin-pack/dune
index b95a7cc6246..36ae897f1cc 100644
--- a/bench/irmin-pack/dune
+++ b/bench/irmin-pack/dune
@@ -1,7 +1,7 @@
 (executables
  (names main)
  (public_names bench-pack)
- (modules main import)
+ (modules main)
  (package irmin-bench)
  (preprocess
   (pps ppx_irmin.internal ppx_repr))
@@ -42,7 +42,8 @@
   trace_replay
   trace_replay_intf
   tezos_history_metrics
-  trace_stat_summary_cb)
+  trace_stat_summary_cb
+  import)
  (preprocess
   (pps ppx_irmin.internal ppx_repr ppx_deriving.enum))
  (libraries
diff --git a/bench/irmin-pack/trace_collection.ml b/bench/irmin-pack/trace_collection.ml
index 20b7b032090..94a51eed8b0 100644
--- a/bench/irmin-pack/trace_collection.ml
+++ b/bench/irmin-pack/trace_collection.ml
@@ -22,6 +22,7 @@
     A module [Make_replayable] has yet to be implemented. *)
 
 open Lwt.Syntax
+module Mtime = Import.Mtime
 
 (** Make state trace collector. *)
 module Make_stat (Store : Irmin.Generic_key.KV) = struct
@@ -200,7 +201,8 @@ module Make_stat (Store : Irmin.Generic_key.KV) = struct
 
   let short_op_end { t0; writer; _ } short_op =
     let duration =
-      Mtime_clock.count t0 |> Mtime.Span.to_s |> Int32.bits_of_float
+      Mtime_clock.count t0 |> fun span ->
+      Mtime.span_to_s span |> Int32.bits_of_float
     in
     let op =
       match short_op with
@@ -238,7 +240,7 @@ module Make_stat (Store : Irmin.Generic_key.KV) = struct
     t.commit_before <- (stats_before, store_before)
 
   let commit_end t tree =
-    let duration = Mtime_clock.count t.t0 |> Mtime.Span.to_s in
+    let duration = Mtime_clock.count t.t0 |> Mtime.span_to_s in
     let duration = duration |> Int32.bits_of_float in
     let stats_after = Bag_of_stats.create t.store_path t.prev_merge_durations in
     t.prev_merge_durations <- Index.Stats.((get ()).merge_durations);
diff --git a/bench/irmin-pack/trace_stat_summary_utils.ml b/bench/irmin-pack/trace_stat_summary_utils.ml
index e35846aed40..8e109b11446 100644
--- a/bench/irmin-pack/trace_stat_summary_utils.ml
+++ b/bench/irmin-pack/trace_stat_summary_utils.ml
@@ -88,7 +88,7 @@ let create_pp_seconds examples =
       Float.neg_infinity examples
   in
   let finite_pp =
-    if absmax >= 60. then fun ppf v -> Mtime.Span.pp_float_s ppf v
+    if absmax >= 60. then fun ppf v -> Fmt.uint64_ns_span ppf (Int64.of_float v)
     else if absmax < 100. *. 1e-12 then fun ppf v ->
       Format.fprintf ppf "%.3e s" v
     else if absmax < 100. *. 1e-9 then fun ppf v ->
diff --git a/irmin-bench.opam b/irmin-bench.opam
index aa60de96936..2e02920cf5d 100644
--- a/irmin-bench.opam
+++ b/irmin-bench.opam
@@ -28,7 +28,7 @@ depends: [
   "progress"     {>="0.2.1"}
   "fpath"        {with-test}
   "bentov"
-  "mtime"        {< "2.0.0"}
+  "mtime"        {>= "2.0.0"}
   "ppx_deriving"
   "alcotest"     {with-test}
   "rusage"
diff --git a/irmin-containers.opam b/irmin-containers.opam
index 672c2acd8fd..c0bb403cc44 100644
--- a/irmin-containers.opam
+++ b/irmin-containers.opam
@@ -20,7 +20,7 @@ depends: [
   "irmin-fs"     {= version}
   "ppx_irmin"    {= version}
   "lwt"          {>= "5.3.0"}
-  "mtime"        {< "2.0.0"}
+  "mtime"        {>= "2.0.0"}
   "alcotest"     {with-test}
   "alcotest-lwt" {with-test}
 ]
diff --git a/irmin-git.opam b/irmin-git.opam
index 5d892b47be6..a50451c80ca 100644
--- a/irmin-git.opam
+++ b/irmin-git.opam
@@ -32,7 +32,7 @@ depends: [
   "uri"
   "mimic"
   "irmin-test" {with-test & = version}
-  "mtime"      {with-test & >= "1.0.0" & < "2.0.0"}
+  "mtime"      {with-test & >= "2.0.0"}
   "alcotest"   {with-test}
   "irmin-watcher" {>= "0.2.0"}
 ]
diff --git a/irmin-pack.opam b/irmin-pack.opam
index cc2483e17d2..ed7460fde9b 100644
--- a/irmin-pack.opam
+++ b/irmin-pack.opam
@@ -21,7 +21,7 @@ depends: [
   "fmt"
   "logs"
   "lwt"          {>= "5.4.0"}
-  "mtime"        {< "2.0.0"}
+  "mtime"        {>= "2.0.0"}
   "cmdliner"
   "optint"       {>= "0.1.0"}
   "checkseum"
diff --git a/irmin-test.opam b/irmin-test.opam
index 58e423b572c..30506a2d8e6 100644
--- a/irmin-test.opam
+++ b/irmin-test.opam
@@ -18,7 +18,7 @@ depends: [
   "ocaml"        {>= "4.02.3"}
   "dune"         {>= "2.9.0"}
   "alcotest-lwt" {>= "1.5.0"}
-  "mtime"        {>= "1.0.0" & < "2.0.0"}
+  "mtime"        {>= "2.0.0"}
   "astring"
   "fmt"
   "jsonm"
diff --git a/irmin.opam b/irmin.opam
index fe3bf05a5ed..f5521eb51e4 100644
--- a/irmin.opam
+++ b/irmin.opam
@@ -27,7 +27,7 @@ depends: [
   "logs"    {>= "0.5.0"}
   "bheap" {>= "2.0.0"}
   "astring"
-  "mtime" {>= "1.0.0" & < "2.0.0"}
+  "mtime" {>= "2.0.0"}
   "bigstringaf" { >= "0.2.0" }
   "ppx_irmin" {= version}
   "hex"      {with-test}
diff --git a/src/irmin-pack/unix/file_manager.ml b/src/irmin-pack/unix/file_manager.ml
index fa296a80a74..88815325fc2 100644
--- a/src/irmin-pack/unix/file_manager.ml
+++ b/src/irmin-pack/unix/file_manager.ml
@@ -885,7 +885,7 @@ struct
       reopen_suffix t ~chunk_start_idx ~chunk_num
         ~appendable_chunk_poff:pl.appendable_chunk_poff
     in
-    let span1 = Mtime_clock.count c0 |> Mtime.Span.to_us in
+    let span1 = Mtime_clock.count c0 |> Mtime.span_to_us in
 
     (* Step 2. Update the control file *)
     let* () =
@@ -928,7 +928,7 @@ struct
               Lower.swap ~volume ~generation ~volume_num:pl.volume_num lower)
     in
 
-    let span2 = Mtime_clock.count c0 |> Mtime.Span.to_us in
+    let span2 = Mtime_clock.count c0 |> Mtime.span_to_us in
     [%log.debug
       "Gc reopen files, update control: %.0fus, %.0fus" span1 (span2 -. span1)];
     Ok ()
diff --git a/src/irmin-pack/unix/store.ml b/src/irmin-pack/unix/store.ml
index 8fbd44f1cdd..17c58e5a343 100644
--- a/src/irmin-pack/unix/store.ml
+++ b/src/irmin-pack/unix/store.ml
@@ -419,7 +419,7 @@ module Maker (Config : Conf.S) = struct
             let node : 'a Node.t = (contents, node) in
             let commit : 'a Commit.t = (node, commit) in
             let on_success res =
-              let s = Mtime_clock.count c0 |> Mtime.Span.to_s in
+              let s = Mtime_clock.count c0 |> Mtime.span_to_s in
               [%log.info "[pack] batch completed in %.6fs" s];
               t.during_batch <- false;
               File_manager.flush t.fm |> Errs.raise_if_error;
diff --git a/src/irmin-test/store_watch.ml b/src/irmin-test/store_watch.ml
index eb14afc329d..5b19ebed0d2 100644
--- a/src/irmin-test/store_watch.ml
+++ b/src/irmin-test/store_watch.ml
@@ -28,7 +28,7 @@ module Make (Log : Logs.LOG) (Zzz : Sleep) (S : Generic_key) = struct
     let sleep_t = min sleep_t 1. in
     Lwt.pause () >>= fun () -> Zzz.sleep sleep_t
 
-  let now_s () = Mtime.Span.to_s (Mtime_clock.elapsed ())
+  let now_s () = Mtime.span_to_s (Mtime_clock.elapsed ())
 
   (* Re-apply [f] at intervals of [sleep_t] while [f] raises exceptions and
      [while_ ()] holds. *)
diff --git a/src/irmin/import.ml b/src/irmin/import.ml
index 6fe68be9472..814f31812af 100644
--- a/src/irmin/import.ml
+++ b/src/irmin/import.ml
@@ -97,6 +97,13 @@ module List = struct
     aux l idx []
 end
 
+module Mtime = struct
+  include Mtime
+
+  let span_to_s span = Mtime.Span.to_float_ns span *. 1e-9
+  let span_to_us span = Mtime.Span.to_float_ns span *. 1e-3
+end
+
 module Seq = struct
   include Seq
   (** @closed *)
diff --git a/src/irmin/logging.ml b/src/irmin/logging.ml
index f398ae412f5..f7e3d186ad7 100644
--- a/src/irmin/logging.ml
+++ b/src/irmin/logging.ml
@@ -36,7 +36,7 @@ let reporter :
     in
     let ppf = match level with Logs.App -> Fmt.stdout | _ -> Fmt.stderr in
     let with_stamp h tags k fmt =
-      let dt = Mtime.Span.to_us (Clock.count start_time) in
+      let dt = Mtime.span_to_us (Clock.count start_time) in
       let source_pos_text, source_pos_colour =
         match tags with
         | None -> (Logs.Src.name src, `Magenta)