Doc improvements (#6)

* add default datetime format, fix default format usage
* fixed format tests
* make reference time configurable
* improve doc

cmd/config.go

@@ -23,6 +23,7 @@ import (
 	"io"
 	"log"
 	"os"
+	"time"
 
 	"github.com/knadh/koanf/providers/posflag"
 	"github.com/knadh/koanf/v2"
@@ -31,7 +32,7 @@ import (
 )
 
 const (
-	VERSIONstring        = "0.0.3"
+	VERSIONstring        = "0.0.4"
 	Usage         string = `This is ts, a timestamp tool.
 
 Usage: ts <time string> [<time string>]
@@ -76,8 +77,11 @@ noon                   Yesterday at 10:15am                 Mon, 02 Jan 2006 15:
 Example durations for second parameter:
 2d1h30m  2 days, one and a half hour
 30m      30 minutes`
+
 	ModeDiff int = iota
 	ModeAdd
+
+	DefaultFormat string = "Mon Jan 02 15:04:05 MST 2006"
 )
 
 type Config struct {
@@ -92,7 +96,10 @@ type Config struct {
 	Args        []string
 	Output      io.Writer
 	Mode        int
-	TZ          string // for unit tests
+
+	// internal flags for [unit] tests
+	tz      string    // has to be set directly in code
+	refTime time.Time // must be set via env var $TSREFTIME
 }
 
 func InitConfig(output io.Writer) (*Config, error) {
@@ -127,11 +134,23 @@ func InitConfig(output io.Writer) (*Config, error) {
 	}
 
 	// fetch values
-	conf := &Config{Output: output}
+	conf := &Config{Output: output, refTime: time.Now()}
 	if err := kloader.Unmarshal("", &conf); err != nil {
 		return nil, fmt.Errorf("error unmarshalling: %w", err)
 	}
 
+	// check internal env var[s], if any
+	reftime, present := os.LookupEnv("TSREFTIME")
+	if present {
+		// e.g: 2014-01-03T00:00:00+01:00
+		ts, err := time.Parse(time.RFC3339Nano, reftime)
+		if err != nil {
+			os.Exit(Die("failed to set reference time from $TSREFTIME", err))
+		}
+
+		conf.refTime = ts
+	}
+
 	// want examples?
 	if conf.Examples {
 		_, err := fmt.Fprintln(output, Examples)

cmd/times.go

@@ -45,9 +45,10 @@ func NewTP(conf *Config, ref ...time.Time) *TimestampProccessor {
 
 	modnow.TimeFormats = append(modnow.TimeFormats, formats...)
 
-	tp := &TimestampProccessor{Config: *conf, Reference: time.Now()}
+	tp := &TimestampProccessor{Config: *conf, Reference: conf.refTime}
 
 	if len(ref) == 1 {
+		// overwritten externally by unit test
 		tp.Reference = ref[0]
 	}
 
@@ -73,9 +74,9 @@ func (tp *TimestampProccessor) Parse(timestamp string) (time.Time, error) {
 		return ts, err
 	}
 
-	if tp.TZ != "" {
+	if tp.tz != "" {
 		// apply custom timezone
-		zone, _ := time.LoadLocation(tp.TZ)
+		zone, _ := time.LoadLocation(tp.tz)
 		ts = ts.In(zone)
 	}
 
@@ -105,7 +106,8 @@ func (tp *TimestampProccessor) SingleTimestamp(timestamp string) error {
 		return err
 	}
 
-	tp.Print(ts)
+	tp.Print(TPdatetime{TimestampProccessor: *tp, Data: ts})
+	//tp.Print(ts)
 
 	return nil
 }

cmd/times_test.go

@@ -73,7 +73,7 @@ func TestParseTimestamps(t *testing.T) {
 		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)
+			tp := NewTP(&Config{Args: []string{tt.input}, Output: &writer, tz: "UTC"}, now)
 
 			// writer.String()
 			ts, err := tp.Parse(tt.input)
@@ -82,7 +82,7 @@ func TestParseTimestamps(t *testing.T) {
 
 			err = tp.ProcessTimestamps()
 			assert.NoError(t, err)
-			assert.EqualValues(t, tt.want.String()+"\n", writer.String())
+			assert.EqualValues(t, tt.want.Format(DefaultFormat)+"\n", writer.String())
 		})
 	}
 }
@@ -148,7 +148,7 @@ func TestAddTimestamps(t *testing.T) {
 
 			err := tp.ProcessTimestamps()
 			assert.NoError(t, err)
-			assert.EqualValues(t, tt.want.String()+"\n", writer.String())
+			assert.EqualValues(t, tt.want.Format(DefaultFormat)+"\n", writer.String())
 		})
 	}
 }

cmd/writer.go

@@ -87,7 +87,7 @@ func (datetime TPdatetime) String() string {
 	case "datetime":
 		fallthrough
 	case "":
-		return datetime.Data.String()
+		return datetime.Data.Format(DefaultFormat)
 	default:
 		return datetime.Data.Format(datetime.Format)
 	}

cmd/writer_test.go

@@ -65,7 +65,7 @@ func TestDatetime(t *testing.T) {
 		{"date", now, "2025-09-25"},
 		{"time", now, "12:30:00"},
 		{"unix", now, "1758803400"},
-		{"datetime", now, "2025-09-25 12:30:00 +0000 UTC"},
+		{"datetime", now, "Thu Sep 25 12:30:00 UTC 2025"},
 	}
 
 	for _, tt := range tests {