diff --git a/cmd/config.go b/cmd/config.go
index 2b10c24..3d0f9e4 100644
--- a/cmd/config.go
+++ b/cmd/config.go
@@ -31,7 +31,7 @@ import (
 )
 
 const (
-	VERSIONstring        = "0.0.2"
+	VERSIONstring        = "0.0.3"
 	Usage         string = `This is ts, a timestamp tool.
 
 Usage: ts <time string> [<time string>]
@@ -92,6 +92,7 @@ type Config struct {
 	Args        []string
 	Output      io.Writer
 	Mode        int
+	TZ          string // for unit tests
 }
 
 func InitConfig(output io.Writer) (*Config, error) {
@@ -135,8 +136,9 @@ func InitConfig(output io.Writer) (*Config, error) {
 	if conf.Examples {
 		_, err := fmt.Fprintln(output, Examples)
 		if err != nil {
-			Die(err)
+			Die("failed write to output file handle", err)
 		}
+
 		os.Exit(0)
 	}
 
diff --git a/cmd/root.go b/cmd/root.go
index b524134..818773e 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -18,12 +18,13 @@ along with this program. If not, see <http://www.gnu.org/licenses/>.
 package cmd
 
 import (
+	"fmt"
 	"io"
-	"log"
+	"os"
 )
 
-func Die(err error) int {
-	log.Fatal("Error: ", err.Error())
+func Die(format string, err error) int {
+	fmt.Fprintf(os.Stderr, format+": %s\n", err)
 
 	return 1
 }
@@ -31,13 +32,14 @@ func Die(err error) int {
 func Main(output io.Writer) int {
 	conf, err := InitConfig(output)
 	if err != nil {
-		return Die(err)
+		fmt.Println(1)
+		return Die("failed to initialize", err)
 	}
 
 	tp := NewTP(conf)
 
 	if err := tp.ProcessTimestamps(); err != nil {
-		return Die(err)
+		return Die("failed to process timestamp[s]", err)
 	}
 
 	return 0
diff --git a/cmd/times.go b/cmd/times.go
index 6398a10..8303fe2 100644
--- a/cmd/times.go
+++ b/cmd/times.go
@@ -20,13 +20,12 @@ package cmd
 import (
 	"errors"
 	"fmt"
-	"log"
 	"regexp"
 	"strconv"
 	"time"
 
+	"github.com/araddon/dateparse"
 	"github.com/ijt/go-anytime"
-	"github.com/itlightning/dateparse"
 	modnow "github.com/jinzhu/now"
 )
 
@@ -60,25 +59,31 @@ func (tp *TimestampProccessor) ProcessTimestamps() error {
 	case 1:
 		return tp.SingleTimestamp(tp.Args[0])
 	case 2:
-		return tp.Calc(tp.Args[0], tp.Args[1])
+		return tp.DualTimestamps(tp.Args[0], tp.Args[1])
 	}
 
 	return nil
 }
 
-func (tp *TimestampProccessor) SingleTimestamp(timestamp string) error {
-	ts, err := tp.Parse(timestamp)
+// a post processor for ParseTimestamp() to apply custom time zone, if any
+func (tp *TimestampProccessor) Parse(timestamp string) (time.Time, error) {
+	ts, err := tp.ParseTimestamp(timestamp)
+
 	if err != nil {
-		return err
+		return ts, err
 	}
 
-	tp.Print(ts)
+	if tp.TZ != "" {
+		// apply custom timezone
+		zone, _ := time.LoadLocation(tp.TZ)
+		ts = ts.In(zone)
+	}
 
-	return nil
+	return ts, nil
 }
 
 // Parse uses 3 different timestamp parser modules to provide maximum flexibility
-func (tp *TimestampProccessor) Parse(timestamp string) (time.Time, error) {
+func (tp *TimestampProccessor) ParseTimestamp(timestamp string) (time.Time, error) {
 	ts, err := anytime.Parse(timestamp, tp.Reference)
 	if err == nil {
 		return ts, nil
@@ -94,7 +99,18 @@ func (tp *TimestampProccessor) Parse(timestamp string) (time.Time, error) {
 	return dateparse.ParseAny(timestamp)
 }
 
-func (tp *TimestampProccessor) Calc(timestampA, timestampB string) error {
+func (tp *TimestampProccessor) SingleTimestamp(timestamp string) error {
+	ts, err := tp.Parse(timestamp)
+	if err != nil {
+		return err
+	}
+
+	tp.Print(ts)
+
+	return nil
+}
+
+func (tp *TimestampProccessor) DualTimestamps(timestampA, timestampB string) error {
 	tsA, err := tp.Parse(timestampA)
 	if err != nil {
 		return err
@@ -112,6 +128,12 @@ func (tp *TimestampProccessor) Calc(timestampA, timestampB string) error {
 		return err
 	}
 
+	tp.CalcDiff(tsA, tsB)
+
+	return nil
+}
+
+func (tp *TimestampProccessor) CalcDiff(tsA time.Time, tsB time.Time) {
 	switch tp.Mode {
 	case ModeDiff:
 		var diff time.Duration
@@ -131,8 +153,6 @@ func (tp *TimestampProccessor) Calc(timestampA, timestampB string) error {
 
 		tp.Print(TPdatetime{TimestampProccessor: *tp, Data: sum})
 	}
-
-	return nil
 }
 
 func (tp *TimestampProccessor) CalcDuration(tsA time.Time, durB time.Duration) {
@@ -151,7 +171,7 @@ func (tp *TimestampProccessor) CalcDuration(tsA time.Time, durB time.Duration) {
 func (tp *TimestampProccessor) Print(ts TimestampWriter) {
 	_, err := fmt.Fprintln(tp.Output, ts.String())
 	if err != nil {
-		log.Fatalf("failed to print to given output handle: %s", err)
+		Die("failed to print to given output handle", err)
 	}
 }
 
diff --git a/cmd/times_test.go b/cmd/times_test.go
index 788d827..9db07b7 100644
--- a/cmd/times_test.go
+++ b/cmd/times_test.go
@@ -65,13 +65,15 @@ func TestParseTimestamps(t *testing.T) {
 		{`One year ago`, now.AddDate(-1, 0, 0)},
 		{`03:15`, dateAtTime(now, 3, 15, 0)},
 		{`Wed Sep 25 12:30:00 PM UTC 2025`, now},
+		{`Wed Sep 25 00:30:00 PM CEST 2025`, now},
+		{`Wed Sep 25 2025 13:30:00 GMT+0100 (GMT Daylight Time)`, now},
 	}
 
 	for _, tt := range datetimes {
 		testname := fmt.Sprintf("parsetimestamp-%s", strings.ReplaceAll(tt.input, " ", "-"))
 		t.Run(testname, func(t *testing.T) {
 			var writer bytes.Buffer
-			tp := NewTP(&Config{Args: []string{tt.input}, Output: &writer}, now)
+			tp := NewTP(&Config{Args: []string{tt.input}, Output: &writer, TZ: "UTC"}, now)
 
 			// writer.String()
 			ts, err := tp.Parse(tt.input)
diff --git a/cmd/writer.go b/cmd/writer.go
index 4710758..b951179 100644
--- a/cmd/writer.go
+++ b/cmd/writer.go
@@ -57,7 +57,7 @@ func (duration TPduration) String() string {
 	// duration, days, hour, min, sec, msec
 	switch duration.Format {
 	case "d", "day", "days":
-		return fmt.Sprintf("%.02f%s", duration.Data.Hours()/24+(duration.Data.Minutes()/60), unit)
+		return fmt.Sprintf("%.02f%s", duration.Data.Hours()/24, unit)
 	case "h", "hour", "hours":
 		return fmt.Sprintf("%.02f%s", duration.Data.Hours(), unit)
 	case "m", "min", "mins", "minutes":
diff --git a/cmd/writer_test.go b/cmd/writer_test.go
new file mode 100644
index 0000000..37e3678
--- /dev/null
+++ b/cmd/writer_test.go
@@ -0,0 +1,81 @@
+/*
+Copyright © 2025 Thomas von Dein
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package cmd
+
+import (
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDuration(t *testing.T) {
+	var tests = []struct {
+		format   string
+		duration time.Duration
+		want     string
+	}{
+		{"day", time.Hour * 24, "1.00 days"},
+		{"dur", time.Hour * 24, "24h0m0s"},
+		{"hour", time.Hour * 24, "24.00 hours"},
+		{"min", time.Minute * 20, "20.00 minutes"},
+		{"min", time.Minute*20 + time.Second*30, "20.50 minutes"},
+		{"sec", time.Second * 30, "30.00 seconds"},
+		{"ms", time.Second * 30, "30000 milliseconds"},
+	}
+
+	for _, tt := range tests {
+		testname := fmt.Sprintf("formatduration-%s", tt.format)
+		t.Run(testname, func(t *testing.T) {
+			tpdur := TPduration{Data: tt.duration}
+			tpdur.Unit = true
+			tpdur.Format = tt.format
+
+			out := tpdur.String()
+			assert.Equal(t, tt.want, out)
+		})
+	}
+}
+
+func TestDatetime(t *testing.T) {
+	var now = time.Date(2025, 9, 25, 12, 30, 00, 0, time.UTC)
+
+	var tests = []struct {
+		format   string
+		datetime time.Time
+		want     string
+	}{
+		{"rfc3339", now, "2025-09-25T12:30:00Z"},
+		{"date", now, "2025-09-25"},
+		{"time", now, "12:30:00"},
+		{"unix", now, "1758803400"},
+		{"datetime", now, "2025-09-25 12:30:00 +0000 UTC"},
+	}
+
+	for _, tt := range tests {
+		testname := fmt.Sprintf("formatdatetime-%s", tt.format)
+		t.Run(testname, func(t *testing.T) {
+			tpdat := TPdatetime{Data: tt.datetime}
+			tpdat.Format = tt.format
+
+			out := tpdat.String()
+			assert.Equal(t, tt.want, out)
+		})
+	}
+}
diff --git a/go.mod b/go.mod
index e86d343..6392998 100644
--- a/go.mod
+++ b/go.mod
@@ -5,6 +5,7 @@ go 1.23.0
 toolchain go1.23.5
 
 require (
+	github.com/araddon/dateparse v0.0.0-20210429162001-6b43995a97de // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/go-viper/mapstructure/v2 v2.4.0 // indirect
 	github.com/ijt/go-anytime v1.9.2 // indirect
@@ -17,7 +18,10 @@ require (
 	github.com/mitchellh/copystructure v1.2.0 // indirect
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/rogpeppe/go-internal v1.14.1 // indirect
 	github.com/spf13/pflag v1.0.10 // indirect
 	github.com/stretchr/testify v1.11.1 // indirect
+	golang.org/x/sys v0.26.0 // indirect
+	golang.org/x/tools v0.26.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
diff --git a/go.sum b/go.sum
index 142938b..c3c2fb2 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,6 @@
+github.com/araddon/dateparse v0.0.0-20210429162001-6b43995a97de h1:FxWPpzIjnTlhPwqqXc4/vE0f7GvRjuAsbW+HOIe8KnA=
+github.com/araddon/dateparse v0.0.0-20210429162001-6b43995a97de/go.mod h1:DCaWoUhZrYW9p1lxo/cm8EmUOOzAPSEZNGF2DK1dJgw=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/go-viper/mapstructure/v2 v2.4.0 h1:EBsztssimR/CONLSZZ04E8qAkxNYq4Qp9LvH92wZUgs=
@@ -16,16 +19,28 @@ github.com/knadh/koanf/providers/posflag v1.0.1 h1:EnMxHSrPkYCFnKgBUl5KBgrjed8gV
 github.com/knadh/koanf/providers/posflag v1.0.1/go.mod h1:3Wn3+YG3f4ljzRyCUgIwH7G0sZ1pMjCOsNBovrbKmAk=
 github.com/knadh/koanf/v2 v2.3.0 h1:Qg076dDRFHvqnKG97ZEsi9TAg2/nFTa9hCdcSa1lvlM=
 github.com/knadh/koanf/v2 v2.3.0/go.mod h1:gRb40VRAbd4iJMYYD5IxZ6hfuopFcXBpc9bbQpZwo28=
+github.com/mattn/go-runewidth v0.0.10/go.mod h1:RAqKPSqVFrSLVXbA8x7dzmKdmGzieGRCM46jaSJTDAk=
 github.com/mitchellh/copystructure v1.2.0 h1:vpKXTN4ewci03Vljg/q9QvCGUDttBOGBIa15WveJJGw=
 github.com/mitchellh/copystructure v1.2.0/go.mod h1:qLl+cE2AmVv+CoeAwDPye/v+N2HKCj9FbZEVFJRxO9s=
 github.com/mitchellh/reflectwalk v1.0.2 h1:G2LzWKi524PWgd3mLHV8Y5k7s6XUvT0Gef6zxSIeXaQ=
 github.com/mitchellh/reflectwalk v1.0.2/go.mod h1:mSTlrgnPZtwu0c4WaC2kGObEpuNDbx0jmZXqmk4esnw=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/rivo/uniseg v0.1.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
+github.com/rogpeppe/go-internal v1.14.1 h1:UQB4HGPB6osV0SQTLymcB4TgvyWu6ZyliaW0tI/otEQ=
+github.com/rogpeppe/go-internal v1.14.1/go.mod h1:MaRKkUm5W0goXpeCfT7UZI6fk/L7L7so1lCWt35ZSgc=
+github.com/scylladb/termtables v0.0.0-20191203121021-c4c0b6d42ff4/go.mod h1:C1a7PQSMz9NShzorzCiG2fk9+xuCgLkPeCvMHYR2OWg=
 github.com/spf13/pflag v1.0.10 h1:4EBh2KAYBwaONj6b2Ye1GiHfwjqyROoF4RwYO+vPwFk=
 github.com/spf13/pflag v1.0.10/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+golang.org/x/sys v0.26.0 h1:KHjCJyddX0LoSTb3J+vWpupP9p0oznkqVk/IfjymZbo=
+golang.org/x/sys v0.26.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/tools v0.26.0 h1:v/60pFQmzmT9ExmjDv2gGIfi3OqfKoEP6I5+umXlbnQ=
+golang.org/x/tools v0.26.0/go.mod h1:TPVVj70c7JJ3WCazhD8OdXcZg/og+b9+tH/KxylGwH0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/main_test.go b/main_test.go
new file mode 100644
index 0000000..56924f9
--- /dev/null
+++ b/main_test.go
@@ -0,0 +1,38 @@
+/*
+Copyright © 2025 Thomas von Dein
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package main
+
+import (
+	"testing"
+
+	"github.com/rogpeppe/go-internal/testscript"
+)
+
+// see https://bitfieldconsulting.com/golang/test-scripts
+
+func TestMain(m *testing.M) {
+	testscript.Main(m, map[string]func(){
+		"ts": main,
+	})
+}
+
+func Test_TS(t *testing.T) {
+	testscript.Run(t, testscript.Params{
+		Dir: "t",
+	})
+}
diff --git a/t/simple.txtar b/t/simple.txtar
new file mode 100644
index 0000000..fac44d1
--- /dev/null
+++ b/t/simple.txtar
@@ -0,0 +1,10 @@
+exec ts -h
+stdout 'This is ts'
+
+exec ts -e
+stdout 'yesterday'
+
+exec ts 3/1/2014
+stdout 2014-01-03
+
+