diff --git a/config.json b/config.json
index fef42c2..9036e7b 100644
--- a/config.json
+++ b/config.json
@@ -105,6 +105,14 @@
         "prerequisites": [],
         "difficulty": 2
       },
+      {
+        "slug": "clock",
+        "name": "Clock",
+        "uuid": "1adaf7d8-7154-4ab9-8db3-7c120f52338c",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4
+      },
       {
         "slug": "collatz-conjecture",
         "name": "Collatz Conjecture",
diff --git a/exercises/practice/clock/.docs/instructions-append.md b/exercises/practice/clock/.docs/instructions-append.md
new file mode 100644
index 0000000..051babd
--- /dev/null
+++ b/exercises/practice/clock/.docs/instructions-append.md
@@ -0,0 +1,13 @@
+# Instructions append
+
+The tests for this exercise expect that your clock will be implemented using a `data declaration` in Pyret.
+If you are unfamiliar with data declarations, [the official documentation][data-declaration] is a good place to start.
+
+As part of the exercise, you'll be comparing values constructed by a `Clock` data variant.
+Because a clock's hours and minutes can roll over in either direction, the following combinations are the same on a clock:  1 hour 1 minute, 0 hours 61 minutes, 25 hours 1 minutes, and 2 hours -59 minutes.
+Pyret's `is` testing operator uses structural equality, which will result in none of these combinations being equal by default.
+To that end, you'll need to define your own equality method for comparing time between values from a Clock data variant.
+If you're unfamiliar with how Pyret handles equality, review the official docs on [equality].
+
+[data-declaration]: https://pyret.org/docs/latest/s_declarations.html#%28part._s~3adata-decl%29
+[equality]: https://pyret.org/docs/latest/equality.html
diff --git a/exercises/practice/clock/.docs/instructions.md b/exercises/practice/clock/.docs/instructions.md
new file mode 100644
index 0000000..a1efc78
--- /dev/null
+++ b/exercises/practice/clock/.docs/instructions.md
@@ -0,0 +1,7 @@
+# Instructions
+
+Implement a clock that handles times without dates.
+
+You should be able to add and subtract minutes to it.
+
+Two clocks that represent the same time should be equal to each other.
diff --git a/exercises/practice/clock/.meta/config.json b/exercises/practice/clock/.meta/config.json
new file mode 100644
index 0000000..17ac696
--- /dev/null
+++ b/exercises/practice/clock/.meta/config.json
@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "clock.arr"
+    ],
+    "test": [
+      "clock-test.arr"
+    ],
+    "example": [
+      ".meta/example.arr"
+    ]
+  },
+  "blurb": "Implement a clock that handles times without dates.",
+  "source": "Pairing session with Erin Drummond",
+  "source_url": "https://twitter.com/ebdrummond"
+}
diff --git a/exercises/practice/clock/.meta/example.arr b/exercises/practice/clock/.meta/example.arr
new file mode 100644
index 0000000..7f11412
--- /dev/null
+++ b/exercises/practice/clock/.meta/example.arr
@@ -0,0 +1,61 @@
+use context essentials2020
+
+provide-types *
+
+import equality as E
+
+data Clock:
+  | clock(hours :: Number, minutes :: Number)
+sharing:
+  method add(self, minutes :: Number) -> Clock:
+    new-clock = clock(self.hours, self.minutes + minutes)
+
+    new-clock.normalize()
+  end,
+  method subtract(self, minutes :: Number) -> Clock:
+    new-clock = clock(self.hours, self.minutes - minutes)
+
+    new-clock.normalize()
+  end,
+  method normalize(self) -> Clock:
+    is-in-range = lam():
+      ((self.minutes >= 0) and (self.minutes < 60))
+      and ((self.hours >= 0) and (self.hours < 24))
+    end
+
+    ask:
+      | not(is-in-range()) then:
+        additional-hours = num-floor(self.minutes / 60)
+        hours = num-modulo((self.hours + additional-hours), 24)
+        minutes = num-modulo(self.minutes, 60)
+
+        clock(hours, minutes)
+      | otherwise:
+        self
+    end
+  end,
+  method _equals(self, other :: Clock, _) -> E.EqualityResult:
+    left = self.normalize()
+    right = other.normalize()
+
+    if (left.hours == right.hours) and (left.minutes == right.minutes):
+      E.Equal
+    else:
+      E.NotEqual("Clocks represent different periods in time", self, other)
+    end
+  end,
+  method to-string(self) -> String:
+    to-two-digits = lam(n):
+      stringified = num-to-string(n)
+      if string-length(stringified) == 1:
+        "0" + stringified
+      else:
+        stringified
+      end
+    end
+
+    normalized = self.normalize()
+
+    to-two-digits(normalized.hours) + ":" + to-two-digits(normalized.minutes)
+  end
+end
\ No newline at end of file
diff --git a/exercises/practice/clock/.meta/tests.toml b/exercises/practice/clock/.meta/tests.toml
new file mode 100644
index 0000000..712c87b
--- /dev/null
+++ b/exercises/practice/clock/.meta/tests.toml
@@ -0,0 +1,166 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[a577bacc-106b-496e-9792-b3083ea8705e]
+description = "Create a new clock with an initial time -> on the hour"
+
+[b5d0c360-3b88-489b-8e84-68a1c7a4fa23]
+description = "Create a new clock with an initial time -> past the hour"
+
+[473223f4-65f3-46ff-a9f7-7663c7e59440]
+description = "Create a new clock with an initial time -> midnight is zero hours"
+
+[ca95d24a-5924-447d-9a96-b91c8334725c]
+description = "Create a new clock with an initial time -> hour rolls over"
+
+[f3826de0-0925-4d69-8ac8-89aea7e52b78]
+description = "Create a new clock with an initial time -> hour rolls over continuously"
+
+[a02f7edf-dfd4-4b11-b21a-86de3cc6a95c]
+description = "Create a new clock with an initial time -> sixty minutes is next hour"
+
+[8f520df6-b816-444d-b90f-8a477789beb5]
+description = "Create a new clock with an initial time -> minutes roll over"
+
+[c75c091b-47ac-4655-8d40-643767fc4eed]
+description = "Create a new clock with an initial time -> minutes roll over continuously"
+
+[06343ecb-cf39-419d-a3f5-dcbae0cc4c57]
+description = "Create a new clock with an initial time -> hour and minutes roll over"
+
+[be60810e-f5d9-4b58-9351-a9d1e90e660c]
+description = "Create a new clock with an initial time -> hour and minutes roll over continuously"
+
+[1689107b-0b5c-4bea-aad3-65ec9859368a]
+description = "Create a new clock with an initial time -> hour and minutes roll over to exactly midnight"
+
+[d3088ee8-91b7-4446-9e9d-5e2ad6219d91]
+description = "Create a new clock with an initial time -> negative hour"
+
+[77ef6921-f120-4d29-bade-80d54aa43b54]
+description = "Create a new clock with an initial time -> negative hour rolls over"
+
+[359294b5-972f-4546-bb9a-a85559065234]
+description = "Create a new clock with an initial time -> negative hour rolls over continuously"
+
+[509db8b7-ac19-47cc-bd3a-a9d2f30b03c0]
+description = "Create a new clock with an initial time -> negative minutes"
+
+[5d6bb225-130f-4084-84fd-9e0df8996f2a]
+description = "Create a new clock with an initial time -> negative minutes roll over"
+
+[d483ceef-b520-4f0c-b94a-8d2d58cf0484]
+description = "Create a new clock with an initial time -> negative minutes roll over continuously"
+
+[1cd19447-19c6-44bf-9d04-9f8305ccb9ea]
+description = "Create a new clock with an initial time -> negative sixty minutes is previous hour"
+
+[9d3053aa-4f47-4afc-bd45-d67a72cef4dc]
+description = "Create a new clock with an initial time -> negative hour and minutes both roll over"
+
+[51d41fcf-491e-4ca0-9cae-2aa4f0163ad4]
+description = "Create a new clock with an initial time -> negative hour and minutes both roll over continuously"
+
+[d098e723-ad29-4ef9-997a-2693c4c9d89a]
+description = "Add minutes -> add minutes"
+
+[b6ec8f38-e53e-4b22-92a7-60dab1f485f4]
+description = "Add minutes -> add no minutes"
+
+[efd349dd-0785-453e-9ff8-d7452a8e7269]
+description = "Add minutes -> add to next hour"
+
+[749890f7-aba9-4702-acce-87becf4ef9fe]
+description = "Add minutes -> add more than one hour"
+
+[da63e4c1-1584-46e3-8d18-c9dc802c1713]
+description = "Add minutes -> add more than two hours with carry"
+
+[be167a32-3d33-4cec-a8bc-accd47ddbb71]
+description = "Add minutes -> add across midnight"
+
+[6672541e-cdae-46e4-8be7-a820cc3be2a8]
+description = "Add minutes -> add more than one day (1500 min = 25 hrs)"
+
+[1918050d-c79b-4cb7-b707-b607e2745c7e]
+description = "Add minutes -> add more than two days"
+
+[37336cac-5ede-43a5-9026-d426cbe40354]
+description = "Subtract minutes -> subtract minutes"
+
+[0aafa4d0-3b5f-4b12-b3af-e3a9e09c047b]
+description = "Subtract minutes -> subtract to previous hour"
+
+[9b4e809c-612f-4b15-aae0-1df0acb801b9]
+description = "Subtract minutes -> subtract more than an hour"
+
+[8b04bb6a-3d33-4e6c-8de9-f5de6d2c70d6]
+description = "Subtract minutes -> subtract across midnight"
+
+[07c3bbf7-ce4d-4658-86e8-4a77b7a5ccd9]
+description = "Subtract minutes -> subtract more than two hours"
+
+[90ac8a1b-761c-4342-9c9c-cdc3ed5db097]
+description = "Subtract minutes -> subtract more than two hours with borrow"
+
+[2149f985-7136-44ad-9b29-ec023a97a2b7]
+description = "Subtract minutes -> subtract more than one day (1500 min = 25 hrs)"
+
+[ba11dbf0-ac27-4acb-ada9-3b853ec08c97]
+description = "Subtract minutes -> subtract more than two days"
+
+[f2fdad51-499f-4c9b-a791-b28c9282e311]
+description = "Compare two clocks for equality -> clocks with same time"
+
+[5d409d4b-f862-4960-901e-ec430160b768]
+description = "Compare two clocks for equality -> clocks a minute apart"
+
+[a6045fcf-2b52-4a47-8bb2-ef10a064cba5]
+description = "Compare two clocks for equality -> clocks an hour apart"
+
+[66b12758-0be5-448b-a13c-6a44bce83527]
+description = "Compare two clocks for equality -> clocks with hour overflow"
+
+[2b19960c-212e-4a71-9aac-c581592f8111]
+description = "Compare two clocks for equality -> clocks with hour overflow by several days"
+
+[6f8c6541-afac-4a92-b0c2-b10d4e50269f]
+description = "Compare two clocks for equality -> clocks with negative hour"
+
+[bb9d5a68-e324-4bf5-a75e-0e9b1f97a90d]
+description = "Compare two clocks for equality -> clocks with negative hour that wraps"
+
+[56c0326d-565b-4d19-a26f-63b3205778b7]
+description = "Compare two clocks for equality -> clocks with negative hour that wraps multiple times"
+
+[c90b9de8-ddff-4ffe-9858-da44a40fdbc2]
+description = "Compare two clocks for equality -> clocks with minute overflow"
+
+[533a3dc5-59a7-491b-b728-a7a34fe325de]
+description = "Compare two clocks for equality -> clocks with minute overflow by several days"
+
+[fff49e15-f7b7-4692-a204-0f6052d62636]
+description = "Compare two clocks for equality -> clocks with negative minute"
+
+[605c65bb-21bd-43eb-8f04-878edf508366]
+description = "Compare two clocks for equality -> clocks with negative minute that wraps"
+
+[b87e64ed-212a-4335-91fd-56da8421d077]
+description = "Compare two clocks for equality -> clocks with negative minute that wraps multiple times"
+
+[822fbf26-1f3b-4b13-b9bf-c914816b53dd]
+description = "Compare two clocks for equality -> clocks with negative hours and minutes"
+
+[e787bccd-cf58-4a1d-841c-ff80eaaccfaa]
+description = "Compare two clocks for equality -> clocks with negative hours and minutes that wrap"
+
+[96969ca8-875a-48a1-86ae-257a528c44f5]
+description = "Compare two clocks for equality -> full clock and zeroed clock"
diff --git a/exercises/practice/clock/clock-test.arr b/exercises/practice/clock/clock-test.arr
new file mode 100644
index 0000000..e310965
--- /dev/null
+++ b/exercises/practice/clock/clock-test.arr
@@ -0,0 +1,383 @@
+use context essentials2020
+
+include file("clock.arr")
+
+#|
+  When working offline, all tests except the first one are skipped by default.
+  Once you get the first test running, unskip the next one until all tests pass locally.
+  Check the block comment below for further details.
+|#
+
+fun create-clock-on-hour():
+  check "Create a new clock with an initial time -> on the hour":
+    clock(8, 0).normalize().to-string() is "08:00"
+  end
+end
+
+fun create-clock-past-hour():
+  check "Create a new clock with an initial time -> past the hour":
+    clock(11, 09).normalize().to-string() is "11:09"
+  end
+end
+
+fun create-clock-midnight():
+  check "Create a new clock with an initial time -> midnight is zero hours":
+    clock(24, 0).normalize().to-string() is "00:00"
+  end
+end
+
+fun create-clock-hours-rollover():
+  check "Create a new clock with an initial time -> hour rolls over":
+    clock(25, 0).normalize().to-string() is "01:00"
+  end
+end
+
+fun create-clock-hours-rollover-multiple():
+  check "Create a new clock with an initial time -> hour rolls over continuously":
+    clock(100, 0).normalize().to-string() is "04:00"
+  end
+end
+
+fun create-clock-sixty-minutes():
+  check "Create a new clock with an initial time -> sixty minutes is next hour":
+    clock(1, 60).normalize().to-string() is "02:00"
+  end
+end
+
+fun create-clock-minutes-rollover():
+  check "Create a new clock with an initial time -> minutes roll over":
+    clock(0, 160).normalize().to-string() is "02:40"
+  end
+end
+
+fun create-clock-minutes-rollover-multiple():
+  check "Create a new clock with an initial time -> minutes roll over continuously":
+    clock(0, 1723).normalize().to-string() is "04:43"
+  end
+end
+
+fun create-clock-rollover():
+  check "Create a new clock with an initial time -> hour and minutes roll over":
+    clock(25, 160).normalize().to-string() is "03:40"
+  end
+end
+
+fun create-clock-rollover-multiple():
+  check "Create a new clock with an initial time -> hour and minutes roll over continuously":
+    clock(201, 3001).normalize().to-string() is "11:01"
+  end
+end
+
+fun create-clock-rollover-to-midnight():
+  check "Create a new clock with an initial time -> hour and minutes roll over to exactly midnight":
+    clock(72, 8640).normalize().to-string() is "00:00"
+  end
+end
+
+fun create-clock-negative-hours():
+  check "Create a new clock with an initial time -> negative hour":
+    clock(-1, 15).normalize().to-string() is "23:15"
+  end
+end
+
+fun create-clock-negative-hours-rollover():
+  check "Create a new clock with an initial time -> negative hour rolls over":
+    clock(-25, 0).normalize().to-string() is "23:00"
+  end
+end
+
+fun create-clock-negative-hours-rollover-multiple():
+  check "Create a new clock with an initial time -> negative hour rolls over continuously":
+    clock(-91, 0).normalize().to-string() is "05:00"
+  end
+end
+
+fun create-clock-negative-minutes():
+  check "Create a new clock with an initial time -> negative minutes":
+    clock(1, -40).normalize().to-string() is "00:20"
+  end
+end
+
+fun create-clock-negative-minutes-rollover():
+  check "Create a new clock with an initial time -> negative minutes roll over":
+    clock(1, -160).normalize().to-string() is "22:20"
+  end
+end
+
+fun create-clock-negative-minutes-rollover-multiple():
+  check "Create a new clock with an initial time -> negative minutes roll over continuously":
+    clock(1, -4820).normalize().to-string() is "16:40"
+  end
+end
+
+fun create-clock-negative-sixty-minutes():
+  check "Create a new clock with an initial time -> negative sixty minutes is previous hour":
+    clock(2, -60).normalize().to-string() is "01:00"
+  end
+end
+
+fun create-clock-negative-rollover():
+  check "Create a new clock with an initial time -> negative hour and minutes both roll over":
+    clock(-25, -160).normalize().to-string() is "20:20"
+  end
+end
+
+fun create-clock-negative-rollover-multiple():
+  check "Create a new clock with an initial time -> negative hour and minutes both roll over continuously":
+    clock(-121, -5810).normalize().to-string() is "22:10"
+  end
+end
+
+fun add-minutes():
+  check "Add minutes -> add minutes":
+    clock(10, 0).add(3).to-string() is "10:03"
+  end
+end
+
+fun add-no-minutes():
+  check "Add minutes -> add no minutes":
+    clock(6, 41).add(0).to-string() is "06:41"
+  end
+end
+
+fun add-to-hours():
+  check "Add minutes -> add to next hour":
+    clock(0, 45).add(40).to-string() is "01:25"
+  end
+end
+
+fun add-to-hours-multiple():
+  check "Add minutes -> add more than one hour":
+    clock(10, 0).add(61).to-string() is "11:01"
+  end
+end
+
+fun add-to-hours-carryover():
+  check "Add minutes -> add more than two hours with carry":
+    clock(0, 45).add(160).to-string() is "03:25"
+  end
+end
+
+fun add-across-midnight():
+  check "Add minutes -> add across midnight":
+    clock(23, 59).add(2).to-string() is "00:01"
+  end
+end
+
+fun add-more-than-one-day():
+  check "Add minutes -> add more than one day (1500 min = 25 hrs)":
+    clock(5, 32).add(1500).to-string() is "06:32"
+  end
+end
+
+fun add-more-than-one-day-multiple():
+  check "Add minutes -> add more than two days":
+    clock(1, 1).add(3500).to-string() is "11:21"
+  end
+end
+
+fun subtract-minutes():
+  check "Subtract minutes -> subtract minutes":
+    clock(10, 3).subtract(3).to-string() is "10:00"
+  end
+end
+
+fun subtract-rollover():
+  check "Subtract minutes -> subtract to previous hour":
+    clock(10, 3).subtract(30).to-string() is "09:33"
+  end
+end
+
+fun subtract-rollover-multiple():
+  check "Subtract minutes -> subtract more than an hour":
+    clock(10, 3).subtract(70).to-string() is "08:53"
+  end
+end
+
+fun subtract-across-midnight():
+  check "Subtract minutes -> subtract across midnight":
+    clock(0, 3).subtract(4).to-string() is "23:59"
+  end
+end
+
+fun subtract-more-than-two-hours():
+  check "Subtract minutes -> subtract more than two hours":
+    clock(0, 0).subtract(160).to-string() is "21:20"
+  end
+end
+
+fun subtract-rollover-borrow():
+  check "Subtract minutes -> subtract more than two hours with borrow":
+    clock(6, 15).subtract(160).to-string() is "03:35"
+  end
+end
+
+fun subtract-more-than-a-day():
+  check "Subtract minutes -> subtract more than one day (1500 min = 25 hrs)":
+    clock(5, 32).subtract(1500).to-string() is "04:32"
+  end
+end
+
+fun subtract-more-than-two-days():
+  check "Subtract minutes -> subtract more than two days":
+    clock(2, 20).subtract(3000).to-string() is "00:20"
+  end
+end
+
+fun equality-same-time():
+  check "Compare two clocks for equality -> clocks with same time":
+    clock(15, 37) is clock(15, 37)
+  end
+end
+
+fun equality-a-minute-apart():
+  check "Compare two clocks for equality -> clocks a minute apart":
+    clock(15, 36) is-not clock(15, 37)
+  end
+end
+
+fun equality-an-hour-apart():
+  check "Compare two clocks for equality -> clocks an hour apart":
+    clock(14, 37) is-not clock(15, 37)
+  end
+end
+
+fun equality-hour-rollover():
+  check "Compare two clocks for equality -> clocks with hour overflow":
+    clock(10, 37) is clock(34, 37)
+  end
+end
+
+fun equality-hour-overflow-multiple():
+  check "Compare two clocks for equality -> clocks with hour overflow by several days":
+    clock(3, 11) is clock(99, 11)
+  end
+end
+
+fun equality-negative-hour():
+  check "Compare two clocks for equality -> clocks with negative hour":
+    clock(22, 40) is clock(-2, 40)
+  end
+end
+
+fun equality-negative-hour-rollover():
+  check "Compare two clocks for equality -> clocks with negative hour that wraps":
+    clock(17, 3) is clock(-31, 3)
+  end
+end
+
+fun equality-negative-hour-rollover-multiple():
+  check "Compare two clocks for equality -> clocks with negative hour that wraps multiple times":
+    clock(13, 49) is clock(-83, 49)
+  end
+end
+
+fun equality-minute-rollover():
+  check "Compare two clocks for equality -> clocks with minute overflow":
+    clock(0, 1) is clock(0, 1441)
+  end
+end
+
+fun equality-rollover-multiple():
+  check "Compare two clocks for equality -> clocks with minute overflow by several days":
+    clock(2, 2) is clock(2, 4322)
+  end
+end
+
+fun equality-negative-minute():
+  check "Compare two clocks for equality -> clocks with negative minute":
+    clock(2, 40) is clock(3, -20)
+  end
+end
+
+fun equality-negative-minute-rollover():
+  check "Compare two clocks for equality -> clocks with negative minute that wraps":
+    clock(4, 10) is clock(5, -1490)
+  end
+end
+
+fun equality-negative-minute-rollover-multiple():
+  check "Compare two clocks for equality -> clocks with negative minute that wraps multiple times":
+    clock(6, 15) is clock(6, -4305)
+  end
+end
+
+fun equality-negative-hour-and-minute():
+  check "Compare two clocks for equality -> clocks with negative hours and minutes":
+    clock(7, 32) is clock(-12, -268)
+  end
+end
+
+fun equality-negative-hours-and-minutes-rollover():
+  check "Compare two clocks for equality -> clocks with negative hours and minutes that wrap":
+    clock(18, 7) is clock(-54, -11513)
+  end
+end
+
+fun equality-full-clock-empty-clock():
+  check "Compare two clocks for equality -> full clock and zeroed clock":
+    clock(24, 0) is clock(0, 0)
+  end
+end
+
+#|
+  Code to run each test. Each line corresponds to a test above and whether it should be run.
+  To mark a test to be run, replace `false` with `true` on that same line after the comma.
+  test(test-a, true) will be run. test(test-a, false) will be skipped.
+|#
+
+data TestRun: test(run, active) end
+
+[list: 
+  test(create-clock-on-hour, true),
+  test(create-clock-past-hour, false),
+  test(create-clock-midnight, false),
+  test(create-clock-hours-rollover, false),
+  test(create-clock-hours-rollover-multiple, false),
+  test(create-clock-sixty-minutes, false),
+  test(create-clock-minutes-rollover, false),
+  test(create-clock-minutes-rollover-multiple, false),
+  test(create-clock-rollover, false),
+  test(create-clock-rollover-multiple, false),
+  test(create-clock-rollover-to-midnight, false),
+  test(create-clock-negative-hours, false),
+  test(create-clock-negative-hours-rollover, false),
+  test(create-clock-negative-hours-rollover-multiple, false),
+  test(create-clock-negative-minutes, false),
+  test(create-clock-negative-minutes-rollover-multiple, false),
+  test(create-clock-negative-sixty-minutes, false),
+  test(create-clock-negative-rollover, false),
+  test(create-clock-negative-rollover-multiple, false),
+  test(add-minutes, false),
+  test(add-no-minutes, false),
+  test(add-to-hours, false),
+  test(add-to-hours-multiple, false),
+  test(add-to-hours-carryover, false),
+  test(add-across-midnight, false),
+  test(add-more-than-one-day, false),
+  test(add-more-than-one-day-multiple, false),
+  test(subtract-minutes, false),
+  test(subtract-rollover, false),
+  test(subtract-rollover-multiple, false),
+  test(subtract-across-midnight, false),
+  test(subtract-more-than-two-hours, false),
+  test(subtract-rollover-borrow, false),
+  test(subtract-more-than-a-day, false),
+  test(subtract-more-than-two-days, false),
+  test(equality-same-time, false),
+  test(equality-a-minute-apart, false),
+  test(equality-an-hour-apart, false),
+  test(equality-hour-rollover, false),
+  test(equality-hour-overflow-multiple, false),
+  test(equality-negative-hour, false),
+  test(equality-negative-hour-rollover, false),
+  test(equality-negative-hour-rollover-multiple, false),
+  test(equality-minute-rollover, false),
+  test(equality-rollover-multiple, false),
+  test(equality-negative-minute, false),
+  test(equality-negative-minute-rollover, false),
+  test(equality-negative-minute-rollover-multiple, false),
+  test(equality-negative-hour-and-minute, false),
+  test(equality-negative-hours-and-minutes-rollover, false),
+  test(equality-full-clock-empty-clock, false)
+].each(lam(t): when t.active: t.run() end end)
\ No newline at end of file
diff --git a/exercises/practice/clock/clock.arr b/exercises/practice/clock/clock.arr
new file mode 100644
index 0000000..e1df6bb
--- /dev/null
+++ b/exercises/practice/clock/clock.arr
@@ -0,0 +1,28 @@
+use context essentials2020
+
+provide-types *
+
+import equality as E
+
+# Replace the ... with your code to pass the tests. Good luck!
+
+data Clock:
+  | clock(hours :: NumInteger, minutes :: NumInteger)
+sharing:
+  method add(self, minutes :: NumInteger) -> Clock:
+    ...
+  end,
+  method subtract(self, minutes :: NumInteger) -> Clock:
+    ...
+  end,
+  method normalize(self) -> Clock:
+    ...
+  end,
+  method _equals(self, other :: Clock, _) -> E.EqualityResult:
+    # The callback argument after other is ignored for this exercise
+    ...
+  end,
+  method to-string(self) -> String:
+    ...
+  end
+end