diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.7.6.2
+
+Fix ISO 8601 date fomatting.  Thanks to Michal @kozak.
+
 ## 0.7.6.1
 
 No user-visible changes
diff --git a/Test/Test.hs b/Test/Test.hs
--- a/Test/Test.hs
+++ b/Test/Test.hs
@@ -1238,6 +1238,11 @@
 testLiterals :: Test
 testLiterals = do
   let testLiteral fn value = testH (pure (fn value)) (`shouldBe` [value])
+      exampleDate = Time.fromGregorian 2018 11 29
+      exampleTime = Time.TimeOfDay 11 22 33
+      exampleUTCTime = Time.UTCTime exampleDate (Time.sinceMidnight exampleTime)
+      exampleDatePadded = Time.fromGregorian 18 11 29
+      exampleUTCTimePadded = Time.UTCTime exampleDatePadded (Time.sinceMidnight exampleTime)
   it "sqlString" $ testLiteral O.sqlString "Hello"
   it "sqlLazyByteString" $ testLiteral O.sqlLazyByteString "Hello"
   it "sqlNumeric" $ testLiteral O.sqlNumeric 3.14159
@@ -1246,13 +1251,21 @@
   it "sqlDouble" $ testLiteral O.sqlDouble 3.14
   it "sqlBool" $ testLiteral O.sqlBool True
   it "sqlUUID" $ testLiteral O.sqlUUID (read "c2cc10e1-57d6-4b6f-9899-38d972112d8c")
-  it "sqlDay" $ testLiteral O.sqlDay (read "2018-11-29")
-  it "sqlUTCTime" $ testLiteral O.sqlUTCTime (read "2018-11-29 11:22:33 UTC")
-  it "sqlLocalTime" $ testLiteral O.sqlLocalTime (read "2018-11-29 11:22:33")
+  it "sqlDay" $ testLiteral O.sqlDay exampleDate
+  it "sqlDayPadded" $ testLiteral O.sqlDay exampleDatePadded
+  it "sqlUTCTime" $ testLiteral O.sqlUTCTime exampleUTCTime
+  it "sqlUTCTimePadded" $ testLiteral O.sqlUTCTime exampleUTCTimePadded
+  it "sqlLocalTime" $ testLiteral O.sqlLocalTime (Time.LocalTime exampleDate exampleTime)
+  it "sqlLocalTimePadded" $ testLiteral O.sqlLocalTime (Time.LocalTime exampleDatePadded exampleTime)
 
   -- ZonedTime has no Eq instance, so we compare on the result of 'zonedTimeToUTC'
   it "sqlZonedTime" $
-    let value = read "2018-11-29 11:22:33 UTC" :: Time.ZonedTime in
+    let value = Time.utcToZonedTime Time.utc exampleUTCTime in
+    testH (pure (O.sqlZonedTime value))
+          (\r -> map Time.zonedTimeToUTC r `shouldBe` [Time.zonedTimeToUTC value])
+
+  it "sqlZonedTimePadded" $
+    let value = Time.utcToZonedTime Time.utc exampleUTCTimePadded in
     testH (pure (O.sqlZonedTime value))
           (\r -> map Time.zonedTimeToUTC r `shouldBe` [Time.zonedTimeToUTC value])
 
diff --git a/opaleye.cabal b/opaleye.cabal
--- a/opaleye.cabal
+++ b/opaleye.cabal
@@ -1,6 +1,6 @@
 name:            opaleye
 copyright:       Copyright (c) 2014-2018 Purely Agile Limited; 2019-2021 Tom Ellis
-version:         0.7.6.1
+version:         0.7.6.2
 synopsis:        An SQL-generating DSL targeting PostgreSQL
 description:     An SQL-generating DSL targeting PostgreSQL.  Allows
                  Postgres queries to be written within Haskell in a
diff --git a/src/Opaleye/Internal/PGTypes.hs b/src/Opaleye/Internal/PGTypes.hs
--- a/src/Opaleye/Internal/PGTypes.hs
+++ b/src/Opaleye/Internal/PGTypes.hs
@@ -13,12 +13,13 @@
 import qualified Data.Text.Lazy.Encoding as LTextEncoding
 import qualified Data.ByteString as SByteString
 import qualified Data.ByteString.Lazy as LByteString
-import qualified Data.Time.Compat as Time
-import qualified Data.Time.Locale.Compat as Locale
+import qualified Data.Time.Format.ISO8601.Compat as Time
 
-unsafePgFormatTime :: Time.FormatTime t => HPQ.Name -> String -> t -> Column c
-unsafePgFormatTime typeName formatString = castToType typeName . format
-  where format = Time.formatTime Locale.defaultTimeLocale formatString
+unsafePgFormatTime :: Time.ISO8601 t => HPQ.Name -> t -> Column c
+unsafePgFormatTime typeName = castToType typeName . format
+    where
+      format  = quote . Time.iso8601Show
+      quote s = "'" ++ s ++ "'"
 
 literalColumn :: forall a. IsSqlType a => HPQ.Literal -> Column a
 literalColumn = Column . HPQ.CastExpr (showSqlType (Proxy :: Proxy a)) . HPQ.ConstExpr
diff --git a/src/Opaleye/Internal/PGTypesExternal.hs b/src/Opaleye/Internal/PGTypesExternal.hs
--- a/src/Opaleye/Internal/PGTypesExternal.hs
+++ b/src/Opaleye/Internal/PGTypesExternal.hs
@@ -102,27 +102,25 @@
 pgUUID = IPT.literalColumn . HPQ.StringLit . UUID.toString
 
 pgDay :: Time.Day -> Column PGDate
-pgDay = IPT.unsafePgFormatTime "date" "'%F'"
+pgDay = IPT.unsafePgFormatTime "date"
 
 pgUTCTime :: Time.UTCTime -> Column PGTimestamptz
-pgUTCTime = IPT.unsafePgFormatTime "timestamptz" "'%FT%T%QZ'"
+pgUTCTime = IPT.unsafePgFormatTime "timestamptz"
 
 pgLocalTime :: Time.LocalTime -> Column PGTimestamp
-pgLocalTime = IPT.unsafePgFormatTime "timestamp" "'%FT%T%Q'"
+pgLocalTime = IPT.unsafePgFormatTime "timestamp"
 
 pgZonedTime :: Time.ZonedTime -> Column PGTimestamptz
-pgZonedTime = IPT.unsafePgFormatTime "timestamptz" "'%FT%T%Q%z'"
+pgZonedTime = IPT.unsafePgFormatTime "timestamptz"
 
 pgTimeOfDay :: Time.TimeOfDay -> Column PGTime
-pgTimeOfDay = IPT.unsafePgFormatTime "time" "'%T%Q'"
+pgTimeOfDay = IPT.unsafePgFormatTime "time"
 
 -- "We recommend not using the type time with time zone"
 -- http://www.postgresql.org/docs/8.3/static/datatype-datetime.html
 
 sqlInterval :: Time.CalendarDiffTime -> Column PGInterval
-sqlInterval = IPT.castToType "interval" . quote . Time.Format.ISO8601.iso8601Show
-    where
-      quote s = "'" ++ s ++ "'"
+sqlInterval = IPT.unsafePgFormatTime "interval"
 
 pgCiStrictText :: CI.CI SText.Text -> Column PGCitext
 pgCiStrictText = IPT.literalColumn . HPQ.StringLit . SText.unpack . CI.original