Add yesterday date shortcut

README.md

@@ -15,8 +15,10 @@ dlog "task progress update"
 dlog amend "corrected task progress update"
 dlog
 dlog log
+dlog log yesterday
 dlog log --date 2026-04-12
 dlog md
+dlog md yesterday
 dlog md --date 2026-04-12
 ```
 
@@ -25,9 +27,9 @@ dlog md --date 2026-04-12
 - `dlog "text"` appends a log entry for today with the current local timestamp.
 - `dlog amend "text"` replaces today's most recent log entry while keeping its original timestamp.
 - `dlog` and `dlog log` show today's logs in reverse chronological order.
-- `dlog log --date YYYY-MM-DD` shows logs for the specified date.
+- `dlog log [YYYY-MM-DD|today|yesterday]` and `dlog log --date [YYYY-MM-DD|today|yesterday]` show logs for the specified date.
 - `dlog md` prints today's logs in Markdown order from oldest to newest.
-- `dlog md --date YYYY-MM-DD` prints logs for the specified date in Markdown order.
+- `dlog md [YYYY-MM-DD|today|yesterday]` and `dlog md --date [YYYY-MM-DD|today|yesterday]` print logs for the specified date in Markdown order.
 - Displayed times use the timezone recorded in each log entry, not the viewer's current local timezone.
 
 ## Examples
@@ -93,6 +95,14 @@ $ dlog md --date 2026-04-11
 - 18:45 previous day task
 ```
 
+Output yesterday's logs as Markdown:
+
+```bash
+$ dlog md yesterday
+# 2026-04-11
+- 18:45 previous day task
+```
+
 ## Storage
 
 - Logs are stored under `~/.dlog`.

cmd/root.go

@@ -48,19 +48,27 @@ func newLogCmd(svc *service.Service, out io.Writer) *cobra.Command {
 	var date string
 
 	cmd := &cobra.Command{
-		Use:   "log",
+		Use:   "log [date]",
 		Short: "Show logs for today or a specified date",
-		Args:  cobra.NoArgs,
+		Args:  cobra.MaximumNArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			var (
 				dayLog *model.DayLog
 				err    error
 			)
 
-			if date == "" {
+			selectedDate := date
+			if selectedDate != "" && len(args) == 1 {
+				return fmt.Errorf("use either --date or a date argument, not both")
+			}
+			if selectedDate == "" && len(args) == 1 {
+				selectedDate = args[0]
+			}
+
+			if selectedDate == "" {
 				dayLog, err = svc.GetTodayLog()
 			} else {
-				dayLog, err = svc.GetLogByDate(date)
+				dayLog, err = svc.GetLogByDate(selectedDate)
 			}
 			if err != nil {
 				return err
@@ -76,7 +84,7 @@ func newLogCmd(svc *service.Service, out io.Writer) *cobra.Command {
 		},
 	}
 
-	cmd.Flags().StringVarP(&date, "date", "d", "", "Show logs for the specified date (YYYY-MM-DD)")
+	cmd.Flags().StringVarP(&date, "date", "d", "", "Show logs for the specified date (YYYY-MM-DD, today, or yesterday)")
 
 	return cmd
 }
@@ -85,19 +93,27 @@ func newMarkdownCmd(svc *service.Service, out io.Writer) *cobra.Command {
 	var date string
 
 	cmd := &cobra.Command{
-		Use:   "md",
+		Use:   "md [date]",
 		Short: "Output logs as Markdown for today or a specified date",
-		Args:  cobra.NoArgs,
+		Args:  cobra.MaximumNArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			var (
 				dayLog *model.DayLog
 				err    error
 			)
 
-			if date == "" {
+			selectedDate := date
+			if selectedDate != "" && len(args) == 1 {
+				return fmt.Errorf("use either --date or a date argument, not both")
+			}
+			if selectedDate == "" && len(args) == 1 {
+				selectedDate = args[0]
+			}
+
+			if selectedDate == "" {
 				dayLog, err = svc.GetTodayLog()
 			} else {
-				dayLog, err = svc.GetLogByDate(date)
+				dayLog, err = svc.GetLogByDate(selectedDate)
 			}
 			if err != nil {
 				return err
@@ -113,7 +129,7 @@ func newMarkdownCmd(svc *service.Service, out io.Writer) *cobra.Command {
 		},
 	}
 
-	cmd.Flags().StringVarP(&date, "date", "d", "", "Output logs for the specified date (YYYY-MM-DD)")
+	cmd.Flags().StringVarP(&date, "date", "d", "", "Output logs for the specified date (YYYY-MM-DD, today, or yesterday)")
 
 	return cmd
 }

cmd/root_test.go

@@ -102,6 +102,28 @@ func TestLogSubcommandShowsSpecifiedDate(t *testing.T) {
 	}
 }
 
+func TestLogSubcommandShowsYesterday(t *testing.T) {
+	current := time.Date(2026, 4, 11, 18, 45, 0, 0, time.FixedZone("JST", 9*60*60))
+	root, stdout, _, _ := newTestRootCmd(t, func() time.Time { return current })
+
+	root.SetArgs([]string{"previous day task"})
+	if err := root.Execute(); err != nil {
+		t.Fatalf("seed previous day log: %v", err)
+	}
+
+	current = time.Date(2026, 4, 12, 9, 0, 0, 0, time.FixedZone("JST", 9*60*60))
+	stdout.Reset()
+	root.SetArgs([]string{"log", "yesterday"})
+	if err := root.Execute(); err != nil {
+		t.Fatalf("execute log yesterday: %v", err)
+	}
+
+	want := "2026-04-11\n\n18:45 previous day task\n"
+	if stdout.String() != want {
+		t.Fatalf("unexpected output:\nwant:\n%s\ngot:\n%s", want, stdout.String())
+	}
+}
+
 func TestLogSubcommandRejectsInvalidDate(t *testing.T) {
 	now := time.Date(2026, 4, 12, 9, 0, 0, 0, time.FixedZone("JST", 9*60*60))
 	root, _, _, _ := newTestRootCmd(t, func() time.Time { return now })
@@ -112,7 +134,22 @@ func TestLogSubcommandRejectsInvalidDate(t *testing.T) {
 		t.Fatalf("expected error")
 	}
 
-	if !strings.Contains(err.Error(), "date must be in YYYY-MM-DD format") {
+	if !strings.Contains(err.Error(), "date must be YYYY-MM-DD, today, or yesterday") {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestLogSubcommandRejectsDateFlagAndArgument(t *testing.T) {
+	now := time.Date(2026, 4, 12, 9, 0, 0, 0, time.FixedZone("JST", 9*60*60))
+	root, _, _, _ := newTestRootCmd(t, func() time.Time { return now })
+
+	root.SetArgs([]string{"log", "-d", "2026-04-12", "yesterday"})
+	err := root.Execute()
+	if err == nil {
+		t.Fatalf("expected error")
+	}
+
+	if !strings.Contains(err.Error(), "use either --date or a date argument, not both") {
 		t.Fatalf("unexpected error: %v", err)
 	}
 }
@@ -159,6 +196,34 @@ func TestMarkdownSubcommandShowsSpecifiedDate(t *testing.T) {
 	}
 }
 
+func TestMarkdownSubcommandShowsYesterday(t *testing.T) {
+	current := time.Date(2026, 4, 11, 10, 3, 0, 0, time.FixedZone("JST", 9*60*60))
+	root, stdout, _, _ := newTestRootCmd(t, func() time.Time { return current })
+
+	root.SetArgs([]string{"first task"})
+	if err := root.Execute(); err != nil {
+		t.Fatalf("seed first log: %v", err)
+	}
+
+	current = time.Date(2026, 4, 11, 11, 10, 0, 0, time.FixedZone("JST", 9*60*60))
+	root.SetArgs([]string{"second task"})
+	if err := root.Execute(); err != nil {
+		t.Fatalf("seed second log: %v", err)
+	}
+
+	current = time.Date(2026, 4, 12, 9, 0, 0, 0, time.FixedZone("JST", 9*60*60))
+	stdout.Reset()
+	root.SetArgs([]string{"md", "yesterday"})
+	if err := root.Execute(); err != nil {
+		t.Fatalf("execute md yesterday: %v", err)
+	}
+
+	want := "# 2026-04-11\n- 10:03 first task\n- 11:10 second task\n"
+	if stdout.String() != want {
+		t.Fatalf("unexpected output:\nwant:\n%s\ngot:\n%s", want, stdout.String())
+	}
+}
+
 func TestMarkdownSubcommandRejectsInvalidDate(t *testing.T) {
 	now := time.Date(2026, 4, 12, 9, 0, 0, 0, time.FixedZone("JST", 9*60*60))
 	root, _, _, _ := newTestRootCmd(t, func() time.Time { return now })
@@ -169,7 +234,7 @@ func TestMarkdownSubcommandRejectsInvalidDate(t *testing.T) {
 		t.Fatalf("expected error")
 	}
 
-	if !strings.Contains(err.Error(), "date must be in YYYY-MM-DD format") {
+	if !strings.Contains(err.Error(), "date must be YYYY-MM-DD, today, or yesterday") {
 		t.Fatalf("unexpected error: %v", err)
 	}
 }

internal/service/service.go

@@ -86,14 +86,30 @@ func (s *Service) GetTodayLog() (*model.DayLog, error) {
 }
 
 func (s *Service) GetLogByDate(date string) (*model.DayLog, error) {
-	parsedDate, err := time.ParseInLocation(dayLayout, date, time.Local)
+	parsedDate, err := s.parseDate(date)
 	if err != nil {
-		return nil, fmt.Errorf("date must be in YYYY-MM-DD format: %q", date)
+		return nil, err
 	}
 
 	return s.getLogByTime(parsedDate)
 }
 
+func (s *Service) parseDate(date string) (time.Time, error) {
+	switch strings.ToLower(strings.TrimSpace(date)) {
+	case "today":
+		return s.now(), nil
+	case "yesterday":
+		return s.now().AddDate(0, 0, -1), nil
+	}
+
+	parsedDate, err := time.ParseInLocation(dayLayout, date, time.Local)
+	if err != nil {
+		return time.Time{}, fmt.Errorf("date must be YYYY-MM-DD, today, or yesterday: %q", date)
+	}
+
+	return parsedDate, nil
+}
+
 func (s *Service) getLogByTime(target time.Time) (*model.DayLog, error) {
 	dayLog, err := s.store.LoadDay(target)
 	if err != nil {

internal/service/service_test.go

@@ -141,6 +141,29 @@ func TestGetLogByDateReturnsSpecifiedDayLog(t *testing.T) {
 	}
 }
 
+func TestGetLogByDateReturnsRelativeDayLog(t *testing.T) {
+	now := time.Date(2026, 4, 11, 18, 45, 0, 0, time.FixedZone("JST", 9*60*60))
+	store := storage.NewStore(t.TempDir())
+	svc := NewWithNow(store, func() time.Time { return now })
+
+	if err := svc.AddTodayLog("previous day task"); err != nil {
+		t.Fatalf("add log: %v", err)
+	}
+
+	now = time.Date(2026, 4, 12, 10, 3, 21, 0, time.FixedZone("JST", 9*60*60))
+	dayLog, err := svc.GetLogByDate("yesterday")
+	if err != nil {
+		t.Fatalf("get log by relative date: %v", err)
+	}
+
+	if dayLog.Date != "2026-04-11" {
+		t.Fatalf("unexpected date: %s", dayLog.Date)
+	}
+	if len(dayLog.Logs) != 1 || dayLog.Logs[0].Text != "previous day task" {
+		t.Fatalf("unexpected logs: %+v", dayLog.Logs)
+	}
+}
+
 func TestGetLogByDateRejectsInvalidFormat(t *testing.T) {
 	now := time.Date(2026, 4, 12, 10, 3, 21, 0, time.FixedZone("JST", 9*60*60))
 	store := storage.NewStore(t.TempDir())
@@ -151,7 +174,7 @@ func TestGetLogByDateRejectsInvalidFormat(t *testing.T) {
 		t.Fatalf("expected error")
 	}
 
-	if !strings.Contains(err.Error(), "date must be in YYYY-MM-DD format") {
+	if !strings.Contains(err.Error(), "date must be YYYY-MM-DD, today, or yesterday") {
 		t.Fatalf("unexpected error: %v", err)
 	}
 }