bump version

* use interface for Duration and Time printing, fix diff ts parsing
* add unit tests and gpl
* added tests, add support for duration diff+add
* bump version
* catch setenv errors
* fix ci job name

.github/workflows/ci.yaml

@@ -1,4 +1,4 @@
-name: build-and-test-gfn
+name: build-and-test
 on: [push]
 jobs:
   build:

.gitignore

@@ -30,3 +30,5 @@ go.work.sum
 # Editor/IDE
 # .idea/
 # .vscode/
+
+ts

Makefile

@@ -16,7 +16,7 @@
 
 #
 # no need to modify anything below
-tool      = gfn
+tool      = ts
 VERSION   = $(shell grep VERSION config.go | head -1 | cut -d '"' -f2)
 archs     = darwin freebsd linux windows
 PREFIX    = /usr/local
@@ -37,11 +37,10 @@ install: buildlocal
 	install -o $(UID) -g $(GID) -m 444 $(tool).1 $(PREFIX)/man/man1/
 
 clean:
-	rm -rf $(tool) coverage.out testdata t/out
+	rm -rf $(tool) coverage.* testdata t/out
 
 test: clean
-	mkdir -p t/out
-	go test ./... $(ARGS)
+	go test -cover ./... $(ARGS)
 
 testlint: test lint
 
@@ -60,7 +59,8 @@ singletest:
 
 cover-report:
 	go test ./... -cover -coverprofile=coverage.out
-	go tool cover -html=coverage.out
+	go tool cover -html=coverage.out -o coverage.html
+	chromium coverage.html
 
 goupdate:
 	go get -t -u=patch ./...
@@ -72,8 +72,8 @@ release:
 	gh release create v$(VERSION) --generate-notes
 
 show-versions: buildlocal
-	@echo "### gfn version:"
-	@./gfn -V
+	@echo "### ts version:"
+	@./ts -V
 
 	@echo
 	@echo "### go module versions:"

README.md

@@ -2,7 +2,7 @@
 
 generic cli timestamp parser and calculator tool
 
-# Usage
+## Usage
 
 ```default
 This is ts, a timestamp tool.
@@ -21,6 +21,32 @@ Usage: ts <time string> [<time string>]
 -e --examples Show examples or supported inputs.
 ```
 
+## Examples
+
+```default
+# diff between to day and yesterday 10 am
+% date && ts today "10am yesterday"
+Wed Sep 24 02:05:03 PM CEST 2025
+14h0m0s
+
+# show timestamp from a couple days ago
+% date && ts "3 days ago"
+Wed Sep 24 02:04:42 PM CEST 2025
+2025-09-21 14:04:42.428910108 +0200 CEST
+
+# show timestamp of one hour and 45 minutes before (-d is the defaul)
+% date && ts -d now 1h45m
+Wed Sep 24 02:04:14 PM CEST 2025
+2025-09-24 12:19:14.932440045 +0200 CEST
+
+# 10 hours from now
+% date && ts --add now 10h 
+Wed Sep 24 02:03:31 PM CEST 2025
+2025-09-25 00:03:31.304518854 +0200 CEST
+```
+
+To see a comprehensive list of supported inputs, call `ts -e`.
+
 ## Installation
 
 The tool does not have any dependencies.  Just download the binary for

cmd/config.go

@@ -1,3 +1,20 @@
+/*
+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 (
@@ -14,12 +31,12 @@ import (
 )
 
 const (
-	VERSIONstring        = "0.0.1"
+	VERSIONstring        = "0.0.3"
 	Usage         string = `This is ts, a timestamp tool.
 
 Usage: ts <time string> [<time string>]
 -d --diff     Calculate difference between two timestamps (default)
--a --add      Add two timestamps (second parameter must be a time)
+-a --add      Add two timestamps (second parameter must be a duration)
 -f --format   For diffs: duration, hour, min, sec, msec
               For timestamps: datetime, rfc3339, date, time, unix, string
               string is a strftime(1) format string. datetime is
@@ -54,7 +71,11 @@ noon                   Yesterday at 10:15am                 Mon, 02 Jan 2006 15:
 1:05pm                 Next dec 22nd at 3pm                 3 days ago                            1999AD
 10:25:10am             Next December 25th at 7:30am UTC-7   Three days ago                        1999 AD
 1:05:10pm              Next December 23rd AT 5:25 PM        1 day from now                        2008CE
-10:25                  Last December 23rd AT 5:25 PM        1 week ago                            2008 CE`
+10:25                  Last December 23rd AT 5:25 PM        1 week ago                            2008 CE
+
+Example durations for second parameter:
+2d1h30m  2 days, one and a half hour
+30m      30 minutes`
 	ModeDiff int = iota
 	ModeAdd
 )
@@ -71,6 +92,7 @@ type Config struct {
 	Args        []string
 	Output      io.Writer
 	Mode        int
+	TZ          string // for unit tests
 }
 
 func InitConfig(output io.Writer) (*Config, error) {
@@ -110,6 +132,16 @@ func InitConfig(output io.Writer) (*Config, error) {
 		return nil, fmt.Errorf("error unmarshalling: %w", err)
 	}
 
+	// want examples?
+	if conf.Examples {
+		_, err := fmt.Fprintln(output, Examples)
+		if err != nil {
+			Die("failed write to output file handle", err)
+		}
+
+		os.Exit(0)
+	}
+
 	// args are timestamps
 	if len(flagset.Args()) == 0 {
 		return nil, errors.New("no timestamp argument[s] specified.\n" + Usage)

cmd/root.go

@@ -1,14 +1,30 @@
+/*
+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"
 	"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
 }
@@ -16,21 +32,14 @@ func Die(err error) int {
 func Main(output io.Writer) int {
 	conf, err := InitConfig(output)
 	if err != nil {
-		return Die(err)
-	}
-
-	if conf.Examples {
-		_, err := fmt.Fprintln(output, Examples)
-		if err != nil {
-			Die(err)
-		}
-		os.Exit(0)
+		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

cmd/times.go

@@ -1,31 +1,57 @@
+/*
+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 (
+	"errors"
 	"fmt"
-	"log"
+	"regexp"
+	"strconv"
 	"time"
 
+	"github.com/araddon/dateparse"
 	"github.com/ijt/go-anytime"
-	"github.com/itlightning/dateparse"
-	"github.com/jinzhu/now"
+	modnow "github.com/jinzhu/now"
 )
 
 type TimestampProccessor struct {
 	Config
+	Reference time.Time
 }
 
-func NewTP(conf *Config) *TimestampProccessor {
+func NewTP(conf *Config, ref ...time.Time) *TimestampProccessor {
+	// we add some pre-defined formats to modnow
 	formats := []string{
 		time.UnixDate, time.RubyDate,
 		time.RFC1123, time.RFC1123Z, time.RFC3339, time.RFC3339Nano,
 		time.RFC822, time.RFC822Z, time.RFC850,
 		"Mon Jan 02 15:04:05 PM MST 2006", // linux date
-		"Mo. 02 Jan. 2006 15:04:05 MST",   // freebsd date (fails, see golang/go/issues/75576)
 	}
 
-	now.TimeFormats = append(now.TimeFormats, formats...)
+	modnow.TimeFormats = append(modnow.TimeFormats, formats...)
 
-	return &TimestampProccessor{Config: *conf}
+	tp := &TimestampProccessor{Config: *conf, Reference: time.Now()}
+
+	if len(ref) == 1 {
+		tp.Reference = ref[0]
+	}
+
+	return tp
 }
 
 func (tp *TimestampProccessor) ProcessTimestamps() error {
@@ -33,12 +59,46 @@ 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
 }
 
+// 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 ts, err
+	}
+
+	if tp.TZ != "" {
+		// apply custom timezone
+		zone, _ := time.LoadLocation(tp.TZ)
+		ts = ts.In(zone)
+	}
+
+	return ts, nil
+}
+
+// Parse uses 3 different timestamp parser modules to provide maximum flexibility
+func (tp *TimestampProccessor) ParseTimestamp(timestamp string) (time.Time, error) {
+	ts, err := anytime.Parse(timestamp, tp.Reference)
+	if err == nil {
+		return ts, nil
+	}
+
+	// anytime failed, try module modnow
+	ts, err = modnow.Parse(timestamp)
+	if err == nil {
+		return ts, nil
+	}
+
+	// modnow failed, try module dateparse
+	return dateparse.ParseAny(timestamp)
+}
+
 func (tp *TimestampProccessor) SingleTimestamp(timestamp string) error {
 	ts, err := tp.Parse(timestamp)
 	if err != nil {
@@ -50,124 +110,109 @@ func (tp *TimestampProccessor) SingleTimestamp(timestamp string) error {
 	return nil
 }
 
-// Parse uses 3 different timestamp parser modules to provide the maximum flexibility
-func (tp *TimestampProccessor) Parse(timestamp string) (time.Time, error) {
-	reference := time.Now()
-	ts, err := anytime.Parse(timestamp, reference)
-	if err == nil {
-		return ts, nil
+func (tp *TimestampProccessor) DualTimestamps(timestampA, timestampB string) error {
+	tsA, err := tp.Parse(timestampA)
+	if err != nil {
+		return err
 	}
 
-	// anytime failed, try module now
-	ts, err = now.Parse(timestamp)
+	durB, err := duration2int(timestampB)
 	if err == nil {
-		return ts, nil
+		// calculate with a duration
+		tp.CalcDuration(tsA, durB)
+		return nil
 	}
 
-	// now failed, try module dateparse
-	return dateparse.ParseAny(timestamp)
+	tsB, err := tp.Parse(timestampB)
+	if err != nil {
+		return err
+	}
+
+	tp.CalcDiff(tsA, tsB)
+
+	return nil
 }
 
-func (tp *TimestampProccessor) Calc(timestampA, timestampB string) error {
-	now := time.Now()
-	tsA, err := anytime.Parse(timestampA, now)
-	if err != nil {
-		return err
-	}
-
-	tsB, err := anytime.Parse(timestampB, now)
-	if err != nil {
-		return err
-	}
-
+func (tp *TimestampProccessor) CalcDiff(tsA time.Time, tsB time.Time) {
 	switch tp.Mode {
 	case ModeDiff:
 		var diff time.Duration
+
+		// avoid negative results
 		if tsA.Unix() > tsB.Unix() {
 			diff = tsA.Sub(tsB)
 		} else {
 			diff = tsB.Sub(tsA)
 		}
-		tp.Print(diff)
+
+		tp.Print(TPduration{TimestampProccessor: *tp, Data: diff})
+
 	case ModeAdd:
 		seconds := (tsB.Hour() * 3600) + (tsB.Minute() * 60) + tsB.Second()
-		tp.Print(tsA.Add(time.Duration(seconds) * time.Second))
-	}
+		sum := tsA.Add(time.Duration(seconds) * time.Second)
 
-	return nil
+		tp.Print(TPdatetime{TimestampProccessor: *tp, Data: sum})
+	}
 }
 
-func (tp *TimestampProccessor) Print(msg any) {
-	var repr string
+func (tp *TimestampProccessor) CalcDuration(tsA time.Time, durB time.Duration) {
+	var datetime time.Time
 
-	switch msg := msg.(type) {
-	case string:
-		repr = msg
-	case time.Time:
-		repr = tp.StringTime(msg)
-	case time.Duration:
-		repr = tp.StringDuration(msg)
+	switch tp.Mode {
+	case ModeDiff:
+		datetime = tsA.Add(-durB)
+	case ModeAdd:
+		datetime = tsA.Add(durB)
 	}
 
-	_, err := fmt.Fprintln(tp.Output, repr)
+	tp.Print(TPdatetime{TimestampProccessor: *tp, Data: datetime})
+}
+
+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)
 	}
 }
 
-func (tp *TimestampProccessor) StringDuration(msg time.Duration) string {
-	var unit string
+/*
+We could use time.ParseDuration(), but this doesn't support days.
 
-	if tp.Unit {
-		switch tp.Format {
-		case "d", "day", "days":
-			unit = " days"
-		case "h", "hour", "hours":
-			unit = " hours"
-		case "m", "min", "mins", "minutes":
-			unit = " minutes"
-		case "s", "sec", "secs", "seconds":
-			unit = " seconds"
-		case "ms", "msec", "msecs", "milliseconds":
-			unit = " milliseconds"
+We  could also  use github.com/xhit/go-str2duration/v2,  which does
+the job,  but it's  just another dependency,  just for  this little
+gem. And  we don't need a  time.Time value.
+
+Convert a  duration into  seconds (int).
+
+	Valid  time units  are "s", "m", "h" and "d".
+
+	Valid inputs: 2h5m (2 hours and 5 min), 10d12h (10 and a half days)
+*/
+func duration2int(duration string) (time.Duration, error) {
+	re := regexp.MustCompile(`(\d+)([dhms])`)
+	seconds := 0
+	found := false
+
+	for _, match := range re.FindAllStringSubmatch(duration, -1) {
+		if len(match) == 3 {
+			found = true
+			v, _ := strconv.Atoi(match[1])
+			switch match[2][0] {
+			case 'd':
+				seconds += v * 86400
+			case 'h':
+				seconds += v * 3600
+			case 'm':
+				seconds += v * 60
+			case 's':
+				seconds += v
+			}
 		}
 	}
 
-	// duration, days, hour, min, sec, msec
-	switch tp.Format {
-	case "d", "day", "days":
-		return fmt.Sprintf("%.02f%s", msg.Hours()/24+(msg.Minutes()/60), unit)
-	case "h", "hour", "hours":
-		return fmt.Sprintf("%.02f%s", msg.Hours(), unit)
-	case "m", "min", "mins", "minutes":
-		return fmt.Sprintf("%.02f%s", msg.Minutes(), unit)
-	case "s", "sec", "secs", "seconds":
-		return fmt.Sprintf("%.02f%s", msg.Seconds(), unit)
-	case "ms", "msec", "msecs", "milliseconds":
-		return fmt.Sprintf("%d%s", msg.Milliseconds(), unit)
-	case "dur", "duration":
-		fallthrough
-	default:
-		return msg.String()
+	if !found {
+		return 0, errors.New("failed to parse duration")
 	}
-}
 
-func (tp *TimestampProccessor) StringTime(msg time.Time) string {
-	// datetime(default), date, time, unix, string
-	switch tp.Format {
-	case "rfc3339":
-		return msg.Format(time.RFC3339)
-	case "date":
-		return msg.Format("2006-01-02")
-	case "time":
-		return msg.Format("03:04:05")
-	case "unix":
-		return fmt.Sprintf("%d", msg.Unix())
-	case "datetime":
-		fallthrough
-	case "":
-		return msg.String()
-	default:
-		return msg.Format(tp.Format)
-	}
+	return time.Duration(seconds) * time.Second, nil
 }

cmd/times_test.go

@@ -0,0 +1,154 @@
+/*
+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 (
+	"bytes"
+	"fmt"
+	"log"
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// reference time for our tests
+var now = time.Date(2025, 9, 25, 12, 30, 00, 0, time.UTC)
+
+// return fixed date at given params
+func dateAtTime(dateFrom time.Time, hour int, min int, sec int) time.Time {
+	t := dateFrom
+	return time.Date(t.Year(), t.Month(), t.Day(), hour, min, sec, 0, t.Location())
+}
+
+func setUTC() {
+	// make sure to have a consistent environment
+	if err := os.Setenv("TZ", "UTC"); err != nil {
+		log.Fatal(err)
+	}
+
+	loc, _ := time.LoadLocation("UTC")
+	time.Local = loc
+}
+
+func TestParseTimestamps(t *testing.T) {
+	setUTC()
+
+	var datetimes = []struct {
+		input string
+		want  time.Time
+	}{
+		// some timestamps from ijt/go-anytime/anytime_test.go
+		{`a minute from now`, now.Add(time.Minute)},
+		{`5 minutes ago`, now.Add(-5 * time.Minute)},
+		{`an hour from now`, now.Add(time.Hour)},
+		{`Yesterday 10am`, dateAtTime(now.AddDate(0, 0, -1), 10, 0, 0)},
+		{`Mon Jan  2 15:04:05 2006`, time.Date(2006, 1, 2, 15, 4, 5, 0, now.Location())},
+		{`1 day from now`, now.Add(24 * time.Hour)},
+		{`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, TZ: "UTC"}, now)
+
+			// writer.String()
+			ts, err := tp.Parse(tt.input)
+			assert.NoError(t, err)
+			assert.Equal(t, tt.want, ts)
+
+			err = tp.ProcessTimestamps()
+			assert.NoError(t, err)
+			assert.EqualValues(t, tt.want.String()+"\n", writer.String())
+		})
+	}
+}
+
+func preDiff(tsA, tsB time.Time) time.Duration {
+	var diff time.Duration
+
+	// avoid negative results
+	if tsA.Unix() > tsB.Unix() {
+		diff = tsA.Sub(tsB)
+	} else {
+		diff = tsB.Sub(tsA)
+	}
+
+	return diff
+}
+
+func TestDiffTimestamps(t *testing.T) {
+	setUTC()
+
+	var datetimes = []struct {
+		A    string
+		B    string
+		want time.Duration
+	}{
+		{`now`, `11:30`, preDiff(now, dateAtTime(now, 11, 30, 00))},
+		{`11:30`, `now`, preDiff(now, dateAtTime(now, 11, 30, 00))},
+	}
+
+	for _, tt := range datetimes {
+		testname := fmt.Sprintf("diff-%s-%s", strings.ReplaceAll(tt.A, " ", "-"), strings.ReplaceAll(tt.B, " ", "-"))
+		t.Run(testname, func(t *testing.T) {
+			var writer bytes.Buffer
+			tp := NewTP(&Config{Args: []string{tt.A, tt.B}, Output: &writer, Mode: ModeDiff}, now)
+
+			err := tp.ProcessTimestamps()
+			assert.NoError(t, err)
+			assert.EqualValues(t, tt.want.String()+"\n", writer.String())
+		})
+	}
+}
+
+func TestAddTimestamps(t *testing.T) {
+	setUTC()
+
+	var datetimes = []struct {
+		A    string
+		B    string
+		want time.Time
+	}{
+		{`now`, `01:30`, dateAtTime(now, 14, 00, 00)},
+		{`now`, `2h`, dateAtTime(now, 14, 30, 00)},
+		{`now`, `12d4h`, dateAtTime(now.Add(time.Hour*24*12), 16, 30, 00)},
+		{`now`, `45m`, dateAtTime(now, 13, 15, 00)},
+		{`now`, `1d10s`, dateAtTime(now.Add(time.Hour*24*1), 12, 30, 10)},
+	}
+
+	for _, tt := range datetimes {
+		testname := fmt.Sprintf("diff-%s-%s", strings.ReplaceAll(tt.A, " ", "-"), strings.ReplaceAll(tt.B, " ", "-"))
+		t.Run(testname, func(t *testing.T) {
+			var writer bytes.Buffer
+			tp := NewTP(&Config{Args: []string{tt.A, tt.B}, Output: &writer, Mode: ModeAdd}, now)
+
+			err := tp.ProcessTimestamps()
+			assert.NoError(t, err)
+			assert.EqualValues(t, tt.want.String()+"\n", writer.String())
+		})
+	}
+}

cmd/writer.go

@@ -0,0 +1,94 @@
+/*
+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"
+	"time"
+)
+
+type TimestampWriter interface {
+	String() string
+}
+
+type TPduration struct {
+	TimestampProccessor
+	Data time.Duration
+}
+
+type TPdatetime struct {
+	TimestampProccessor
+	Data time.Time
+}
+
+func (duration TPduration) String() string {
+	var unit string
+
+	if duration.Unit {
+		switch duration.Format {
+		case "d", "day", "days":
+			unit = " days"
+		case "h", "hour", "hours":
+			unit = " hours"
+		case "m", "min", "mins", "minutes":
+			unit = " minutes"
+		case "s", "sec", "secs", "seconds":
+			unit = " seconds"
+		case "ms", "msec", "msecs", "milliseconds":
+			unit = " milliseconds"
+		}
+	}
+
+	// duration, days, hour, min, sec, msec
+	switch duration.Format {
+	case "d", "day", "days":
+		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":
+		return fmt.Sprintf("%.02f%s", duration.Data.Minutes(), unit)
+	case "s", "sec", "secs", "seconds":
+		return fmt.Sprintf("%.02f%s", duration.Data.Seconds(), unit)
+	case "ms", "msec", "msecs", "milliseconds":
+		return fmt.Sprintf("%d%s", duration.Data.Milliseconds(), unit)
+	case "dur", "duration":
+		fallthrough
+	default:
+		return duration.Data.String()
+	}
+}
+
+func (datetime TPdatetime) String() string {
+	// datetime(default), date, time, unix, string
+	switch datetime.Format {
+	case "rfc3339":
+		return datetime.Data.Format(time.RFC3339)
+	case "date":
+		return datetime.Data.Format("2006-01-02")
+	case "time":
+		return datetime.Data.Format("03:04:05")
+	case "unix":
+		return fmt.Sprintf("%d", datetime.Data.Unix())
+	case "datetime":
+		fallthrough
+	case "":
+		return datetime.Data.String()
+	default:
+		return datetime.Data.Format(datetime.Format)
+	}
+}

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)
+		})
+	}
+}

go.mod

@@ -5,6 +5,8 @@ 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
 	github.com/ijt/goparsify v0.0.0-20221203142333-3a5276334b8d // indirect
@@ -15,5 +17,11 @@ require (
 	github.com/knadh/koanf/v2 v2.3.0 // indirect
 	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
 )

go.sum

@@ -1,3 +1,8 @@
+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=
 github.com/go-viper/mapstructure/v2 v2.4.0/go.mod h1:oJDH3BJKyqBA2TXFhDsKDGDTlndYOZ6rGS0BRZIxGhM=
 github.com/ijt/go-anytime v1.9.2 h1:DmYgVwUiFPNR+n6c1T5P070tlGATRZG4aYNJs6XDUfU=
@@ -14,9 +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=

main.go

@@ -1,3 +1,20 @@
+/*
+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 (

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",
+	})
+}

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
+
+