diff --git a/cmd/config.go b/cmd/config.go
index e8b18b9..7bb6e66 100644
--- a/cmd/config.go
+++ b/cmd/config.go
@@ -23,6 +23,7 @@ import (
 	"io"
 	"log"
 	"os"
+	"time"
 
 	"github.com/knadh/koanf/providers/posflag"
 	"github.com/knadh/koanf/v2"
@@ -80,7 +81,7 @@ Example durations for second parameter:
 	ModeDiff int = iota
 	ModeAdd
 
-	DefaultFormat string = "Mon Jan 02 15:04:05 MST"
+	DefaultFormat string = "Mon Jan 02 15:04:05 MST 2006"
 )
 
 type Config struct {
@@ -95,7 +96,10 @@ type Config struct {
 	Args        []string
 	Output      io.Writer
 	Mode        int
-	TZ          string // for unit tests
+
+	// internal flags for [unit] tests
+	tz      string
+	refTime time.Time
 }
 
 func InitConfig(output io.Writer) (*Config, error) {
diff --git a/cmd/times.go b/cmd/times.go
index 826855f..f4b6c57 100644
--- a/cmd/times.go
+++ b/cmd/times.go
@@ -73,9 +73,9 @@ 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)
 	}
 
diff --git a/cmd/times_test.go b/cmd/times_test.go
index 9db07b7..8e9835b 100644
--- a/cmd/times_test.go
+++ b/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())
 		})
 	}
 }
diff --git a/cmd/writer_test.go b/cmd/writer_test.go
index 37e3678..110b9a4 100644
--- a/cmd/writer_test.go
+++ b/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 {
diff --git a/t/simple.txtar b/t/simple.txtar
index fac44d1..988f91e 100644
--- a/t/simple.txtar
+++ b/t/simple.txtar
@@ -5,6 +5,6 @@ exec ts -e
 stdout 'yesterday'
 
 exec ts 3/1/2014
-stdout 2014-01-03
+stdout 'Fri Jan 03'