diff --git a/cmd/zenity/main.go b/cmd/zenity/main.go
index 4bca1f6..fe43981 100644
--- a/cmd/zenity/main.go
+++ b/cmd/zenity/main.go
@@ -116,6 +116,8 @@ func main() {
 	validateFlags()
 	opts := loadFlags()
 	zenutil.Command = true
+	zenutil.DateUTS35 = func() (string, error) { return strftime.UTS35(zenutil.DateFormat) }
+	zenutil.DateParse = func(s string) (time.Time, error) { return strftime.Parse(zenutil.DateFormat, s) }
 	if unixeol {
 		zenutil.LineBreak = "\n"
 	}
diff --git a/date_darwin.go b/date_darwin.go
index 7bb8b7f..a97f11e 100644
--- a/date_darwin.go
+++ b/date_darwin.go
@@ -3,7 +3,6 @@ package zenity
 import (
 	"time"
 
-	"github.com/ncruces/go-strftime"
 	"github.com/ncruces/zenity/internal/zenutil"
 )
 
@@ -11,7 +10,7 @@ func calendar(text string, opts options) (t time.Time, err error) {
 	var date zenutil.Date
 
 	date.OK, date.Cancel, date.Extra = getAlertButtons(opts)
-	date.Format, err = strftime.UTS35(zenutil.DateFormat)
+	date.Format, err = zenutil.DateUTS35()
 	if err != nil {
 		return
 	}
@@ -32,5 +31,5 @@ func calendar(text string, opts options) (t time.Time, err error) {
 	if err != nil {
 		return
 	}
-	return strftime.Parse(zenutil.DateFormat, str)
+	return zenutil.DateParse(str)
 }
diff --git a/date_unix.go b/date_unix.go
index 90d95de..fc043ef 100644
--- a/date_unix.go
+++ b/date_unix.go
@@ -6,7 +6,6 @@ import (
 	"strconv"
 	"time"
 
-	"github.com/ncruces/go-strftime"
 	"github.com/ncruces/zenity/internal/zenutil"
 )
 
@@ -28,5 +27,5 @@ func calendar(text string, opts options) (time.Time, error) {
 	if err != nil {
 		return time.Time{}, err
 	}
-	return strftime.Parse(zenutil.DateFormat, str)
+	return zenutil.DateParse(str)
 }
diff --git a/go.mod b/go.mod
index fb75722..6440e03 100644
--- a/go.mod
+++ b/go.mod
@@ -9,7 +9,7 @@ require (
 	github.com/randall77/makefat v0.0.0-20210315173500-7ddd0e42c844
 	go.uber.org/goleak v1.1.12 // test
 	golang.org/x/image v0.0.0-20220413100746-70e8d0d3baa9
-	golang.org/x/sys v0.0.0-20220429233432-b5fbb4746d32
+	golang.org/x/sys v0.0.0-20220502124256-b6088ccd6cba
 )
 
 require (
diff --git a/go.sum b/go.sum
index 64b29ea..9ab6230 100644
--- a/go.sum
+++ b/go.sum
@@ -42,8 +42,8 @@ golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210330210617-4fbd30eecc44/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210510120138-977fb7262007/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220429233432-b5fbb4746d32 h1:Js08h5hqB5xyWR789+QqueR6sDE8mk+YvpETZ+F6X9Y=
-golang.org/x/sys v0.0.0-20220429233432-b5fbb4746d32/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220502124256-b6088ccd6cba h1:AyHWHCBVlIYI5rgEM3o+1PLd0sLPcIAoaUckGQMaWtw=
+golang.org/x/sys v0.0.0-20220502124256-b6088ccd6cba/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
diff --git a/internal/zenutil/env.go b/internal/zenutil/env.go
index 43ff36c..4242b67 100644
--- a/internal/zenutil/env.go
+++ b/internal/zenutil/env.go
@@ -1,6 +1,8 @@
 // Package zenutil is internal. DO NOT USE.
 package zenutil
 
+import "time"
+
 // These are internal.
 const (
 	ErrCanceled    = stringErr("dialog canceled")
@@ -8,6 +10,16 @@ const (
 	ErrUnsupported = stringErr("unsupported option")
 )
 
+// These are internal.
+var (
+	Command bool
+	Timeout int
+
+	DateFormat = "%Y-%m-%d"
+	DateUTS35  = func() (string, error) { return "yyyy-MM-dd", nil }
+	DateParse  = func(s string) (time.Time, error) { return time.Parse("2006-01-02", s) }
+)
+
 type stringErr string
 
 func (e stringErr) Error() string { return string(e) }
diff --git a/internal/zenutil/env_darwin.go b/internal/zenutil/env_darwin.go
index 0b0af9f..39b99f8 100644
--- a/internal/zenutil/env_darwin.go
+++ b/internal/zenutil/env_darwin.go
@@ -2,9 +2,6 @@ package zenutil
 
 // These are internal.
 var (
-	Command    bool
-	Timeout    int
-	Separator  = "\x00"
-	LineBreak  = "\n"
-	DateFormat = "%F"
+	Separator = "\x00"
+	LineBreak = "\n"
 )
diff --git a/internal/zenutil/env_unix.go b/internal/zenutil/env_unix.go
index 7c6336f..ad4003b 100644
--- a/internal/zenutil/env_unix.go
+++ b/internal/zenutil/env_unix.go
@@ -4,9 +4,6 @@ package zenutil
 
 // These are internal.
 var (
-	Command    bool
-	Timeout    int
-	Separator  = "\x1e"
-	LineBreak  = "\n"
-	DateFormat = "%F"
+	Separator = "\x1e"
+	LineBreak = "\n"
 )
diff --git a/internal/zenutil/env_windows.go b/internal/zenutil/env_windows.go
index 993ea6c..e8e1894 100644
--- a/internal/zenutil/env_windows.go
+++ b/internal/zenutil/env_windows.go
@@ -2,9 +2,6 @@ package zenutil
 
 // These are internal.
 var (
-	Command    bool
-	Timeout    int
-	Separator  string
-	LineBreak  = "\r\n"
-	DateFormat = "%F"
+	Separator string
+	LineBreak = "\r\n"
 )