diff --git a/opal-task/internal/engine/annotate_test.go b/opal-task/internal/engine/annotate_test.go
new file mode 100644
index 0000000..0e525f3
--- /dev/null
+++ b/opal-task/internal/engine/annotate_test.go
@@ -0,0 +1,178 @@
+package engine
+
+import (
+	"testing"
+	"time"
+)
+
+func TestAnnotate(t *testing.T) {
+	task, err := CreateTask("Annotation test task")
+	if err != nil {
+		t.Fatalf("Failed to create task: %v", err)
+	}
+	defer func() { task.Delete(true) }()
+
+	// Initially no annotations
+	if len(task.Annotations) != 0 {
+		t.Fatalf("new task should have 0 annotations, got %d", len(task.Annotations))
+	}
+
+	// Add first annotation
+	if err := task.Annotate("First note"); err != nil {
+		t.Fatalf("Annotate failed: %v", err)
+	}
+	if len(task.Annotations) != 1 {
+		t.Fatalf("expected 1 annotation, got %d", len(task.Annotations))
+	}
+	if task.Annotations[0].Text != "First note" {
+		t.Errorf("annotation text = %q, want %q", task.Annotations[0].Text, "First note")
+	}
+	if task.Annotations[0].Timestamp == 0 {
+		t.Error("annotation timestamp should be non-zero")
+	}
+
+	// Add second annotation
+	if err := task.Annotate("Second note"); err != nil {
+		t.Fatalf("Annotate failed: %v", err)
+	}
+	if len(task.Annotations) != 2 {
+		t.Fatalf("expected 2 annotations, got %d", len(task.Annotations))
+	}
+	if task.Annotations[1].Text != "Second note" {
+		t.Errorf("second annotation text = %q, want %q", task.Annotations[1].Text, "Second note")
+	}
+}
+
+func TestAnnotate_Persistence(t *testing.T) {
+	task, err := CreateTask("Annotation persistence test")
+	if err != nil {
+		t.Fatalf("Failed to create task: %v", err)
+	}
+	defer func() { task.Delete(true) }()
+
+	if err := task.Annotate("Persisted note"); err != nil {
+		t.Fatalf("Annotate failed: %v", err)
+	}
+
+	// Reload from DB
+	loaded, err := GetTask(task.UUID)
+	if err != nil {
+		t.Fatalf("GetTask failed: %v", err)
+	}
+	if len(loaded.Annotations) != 1 {
+		t.Fatalf("loaded task: expected 1 annotation, got %d", len(loaded.Annotations))
+	}
+	if loaded.Annotations[0].Text != "Persisted note" {
+		t.Errorf("loaded annotation text = %q, want %q", loaded.Annotations[0].Text, "Persisted note")
+	}
+}
+
+func TestAnnotate_TimestampOrdering(t *testing.T) {
+	origTimeNow := timeNow
+	defer func() { timeNow = origTimeNow }()
+
+	task, err := CreateTask("Timestamp ordering test")
+	if err != nil {
+		t.Fatalf("Failed to create task: %v", err)
+	}
+	defer func() { timeNow = origTimeNow; task.Delete(true) }()
+
+	// Add annotations at different times
+	t1 := time.Date(2026, 1, 1, 10, 0, 0, 0, time.UTC)
+	t2 := time.Date(2026, 1, 1, 11, 0, 0, 0, time.UTC)
+
+	timeNow = func() time.Time { return t1 }
+	task.Annotate("First")
+
+	timeNow = func() time.Time { return t2 }
+	task.Annotate("Second")
+
+	if task.Annotations[0].Timestamp >= task.Annotations[1].Timestamp {
+		t.Error("annotations should be in chronological order")
+	}
+}
+
+func TestDenotate(t *testing.T) {
+	task, err := CreateTask("Denotate test task")
+	if err != nil {
+		t.Fatalf("Failed to create task: %v", err)
+	}
+	defer func() { task.Delete(true) }()
+
+	task.Annotate("First")
+	task.Annotate("Second")
+	task.Annotate("Third")
+
+	// Denotate removes the last
+	removed, err := task.Denotate()
+	if err != nil {
+		t.Fatalf("Denotate failed: %v", err)
+	}
+	if removed.Text != "Third" {
+		t.Errorf("removed text = %q, want %q", removed.Text, "Third")
+	}
+	if len(task.Annotations) != 2 {
+		t.Fatalf("expected 2 annotations after denotate, got %d", len(task.Annotations))
+	}
+
+	// Remove second
+	removed, err = task.Denotate()
+	if err != nil {
+		t.Fatalf("Denotate failed: %v", err)
+	}
+	if removed.Text != "Second" {
+		t.Errorf("removed text = %q, want %q", removed.Text, "Second")
+	}
+
+	// Remove first
+	removed, err = task.Denotate()
+	if err != nil {
+		t.Fatalf("Denotate failed: %v", err)
+	}
+	if removed.Text != "First" {
+		t.Errorf("removed text = %q, want %q", removed.Text, "First")
+	}
+
+	// Nothing left — should error
+	_, err = task.Denotate()
+	if err == nil {
+		t.Error("Denotate on empty annotations should return error")
+	}
+}
+
+func TestDenotate_Empty(t *testing.T) {
+	task, err := CreateTask("Denotate empty test")
+	if err != nil {
+		t.Fatalf("Failed to create task: %v", err)
+	}
+	defer func() { task.Delete(true) }()
+
+	_, err = task.Denotate()
+	if err == nil {
+		t.Error("Denotate on task with no annotations should return error")
+	}
+}
+
+func TestDenotate_Persistence(t *testing.T) {
+	task, err := CreateTask("Denotate persistence test")
+	if err != nil {
+		t.Fatalf("Failed to create task: %v", err)
+	}
+	defer func() { task.Delete(true) }()
+
+	task.Annotate("Keep this")
+	task.Annotate("Remove this")
+	task.Denotate()
+
+	// Reload and verify
+	loaded, err := GetTask(task.UUID)
+	if err != nil {
+		t.Fatalf("GetTask failed: %v", err)
+	}
+	if len(loaded.Annotations) != 1 {
+		t.Fatalf("loaded: expected 1 annotation, got %d", len(loaded.Annotations))
+	}
+	if loaded.Annotations[0].Text != "Keep this" {
+		t.Errorf("remaining annotation = %q, want %q", loaded.Annotations[0].Text, "Keep this")
+	}
+}
diff --git a/opal-task/internal/engine/dateparse.go b/opal-task/internal/engine/dateparse.go
index ec9d63a..14a4e74 100644
--- a/opal-task/internal/engine/dateparse.go
+++ b/opal-task/internal/engine/dateparse.go
@@ -54,7 +54,7 @@ func (p *DateParser) parseDateOnly(s string) (time.Time, error) {
 	}
 
 	// Try ISO format first
-	if t, err := time.Parse("2006-01-02", s); err == nil {
+	if t, err := time.ParseInLocation("2006-01-02", s, p.base.Location()); err == nil {
 		return t, nil
 	}
 
diff --git a/opal-task/internal/engine/dateparse_test.go b/opal-task/internal/engine/dateparse_test.go
index 80d8f6c..b764790 100644
--- a/opal-task/internal/engine/dateparse_test.go
+++ b/opal-task/internal/engine/dateparse_test.go
@@ -226,6 +226,127 @@ func TestParseDateWithTime(t *testing.T) {
 	}
 }
 
+func TestSplitDateTime(t *testing.T) {
+	base := time.Date(2026, 1, 5, 12, 0, 0, 0, time.UTC)
+	parser := NewDateParser(base, time.Monday)
+
+	tests := []struct {
+		name     string
+		input    string
+		wantDate string
+		wantTime string
+		wantHas  bool
+	}{
+		{"plain weekday", "mon", "mon", "", false},
+		{"plain date", "2026-01-15", "2026-01-15", "", false},
+		{"weekday+HHMM", "mon:0800", "mon", "0800", true},
+		{"weekday+HH:MM", "mon:15:35", "mon", "15:35", true},
+		{"date+HHMM", "21jan:1430", "21jan", "1430", true},
+		{"just time HH:MM", "15:35", "", "15:35", true},
+		{"tomorrow+time", "tomorrow:0800", "tomorrow", "0800", true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			dateStr, timeStr, hasTime := parser.splitDateTime(tt.input)
+			if hasTime != tt.wantHas {
+				t.Errorf("hasTime = %v, want %v", hasTime, tt.wantHas)
+			}
+			if hasTime {
+				if dateStr != tt.wantDate {
+					t.Errorf("dateStr = %q, want %q", dateStr, tt.wantDate)
+				}
+				if timeStr != tt.wantTime {
+					t.Errorf("timeStr = %q, want %q", timeStr, tt.wantTime)
+				}
+			}
+		})
+	}
+}
+
+func TestParseISODate(t *testing.T) {
+	// Use a non-UTC timezone to verify ISO dates respect the parser's location
+	loc := time.FixedZone("UTC+10", 10*60*60)
+	base := time.Date(2026, 1, 5, 12, 0, 0, 0, loc)
+	parser := NewDateParser(base, time.Monday)
+
+	result, err := parser.ParseDate("2026-02-20")
+	if err != nil {
+		t.Fatalf("Failed to parse ISO date: %v", err)
+	}
+
+	expected := time.Date(2026, 2, 20, 0, 0, 0, 0, loc)
+	if !result.Equal(expected) {
+		t.Errorf("Expected %v, got %v", expected, result)
+	}
+	if result.Location() != loc {
+		t.Errorf("Expected location %v, got %v", loc, result.Location())
+	}
+}
+
+func TestParseDateInvalid(t *testing.T) {
+	base := time.Date(2026, 1, 5, 12, 0, 0, 0, time.UTC)
+	parser := NewDateParser(base, time.Monday)
+
+	invalids := []string{
+		"notadate",
+		"xyz123",
+		"",
+		"32jan",
+		"feb30",
+	}
+
+	for _, input := range invalids {
+		t.Run(input, func(t *testing.T) {
+			_, err := parser.ParseDate(input)
+			if err == nil && input != "" {
+				// Some of these might parse as durations or keywords
+				// but truly invalid ones should error
+				t.Logf("ParseDate(%q) did not error (may be valid as keyword/duration)", input)
+			}
+		})
+	}
+}
+
+func TestNextWeekday_Exhaustive(t *testing.T) {
+	// Test all 7 starting days × 7 target days
+	// Mon Jan 5 2026
+	monday := time.Date(2026, 1, 5, 12, 0, 0, 0, time.UTC)
+
+	allDays := []time.Weekday{
+		time.Sunday, time.Monday, time.Tuesday, time.Wednesday,
+		time.Thursday, time.Friday, time.Saturday,
+	}
+
+	for fromOffset := 0; fromOffset < 7; fromOffset++ {
+		from := monday.AddDate(0, 0, fromOffset)
+		parser := NewDateParser(from, time.Monday)
+
+		for _, target := range allDays {
+			t.Run(from.Weekday().String()+"_to_"+target.String(), func(t *testing.T) {
+				result := parser.nextWeekday(target)
+
+				// Must land on the correct weekday
+				if result.Weekday() != target {
+					t.Errorf("weekday = %v, want %v", result.Weekday(), target)
+				}
+
+				// Must be 1-7 days in the future
+				fromMidnight := time.Date(from.Year(), from.Month(), from.Day(), 0, 0, 0, 0, from.Location())
+				days := int(result.Sub(fromMidnight).Hours() / 24)
+				if days < 1 || days > 7 {
+					t.Errorf("days ahead = %d, want 1-7 (from %v to %v)", days, from, result)
+				}
+
+				// Same weekday should always be 7 days ahead
+				if from.Weekday() == target && days != 7 {
+					t.Errorf("same weekday should be 7 days, got %d", days)
+				}
+			})
+		}
+	}
+}
+
 func TestExpandedDurationFormats(t *testing.T) {
 	tests := []struct {
 		name     string
diff --git a/opal-task/internal/engine/history_test.go b/opal-task/internal/engine/history_test.go
new file mode 100644
index 0000000..74d01f4
--- /dev/null
+++ b/opal-task/internal/engine/history_test.go
@@ -0,0 +1,328 @@
+package engine
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestParseChangeData(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected map[string]string
+	}{
+		{
+			"basic key-value pairs",
+			"description: Buy groceries\nstatus: pending\npriority: H",
+			map[string]string{"description": "Buy groceries", "status": "pending", "priority": "H"},
+		},
+		{
+			"empty string",
+			"",
+			map[string]string{},
+		},
+		{
+			"whitespace only",
+			"  \n  \n  ",
+			map[string]string{},
+		},
+		{
+			"value with colon",
+			"description: Fix bug: crash on startup\nstatus: pending",
+			map[string]string{"description": "Fix bug: crash on startup", "status": "pending"},
+		},
+		{
+			"trailing newlines",
+			"description: Test\nstatus: pending\n\n",
+			map[string]string{"description": "Test", "status": "pending"},
+		},
+		{
+			"no separator",
+			"this line has no colon-space separator",
+			map[string]string{},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := parseChangeData(tt.input)
+			if len(result) != len(tt.expected) {
+				t.Errorf("len = %d, want %d; got %v", len(result), len(tt.expected), result)
+				return
+			}
+			for k, v := range tt.expected {
+				if result[k] != v {
+					t.Errorf("key %q = %q, want %q", k, result[k], v)
+				}
+			}
+		})
+	}
+}
+
+func TestDiffFields(t *testing.T) {
+	tests := []struct {
+		name          string
+		prev          map[string]string
+		curr          map[string]string
+		expectChanges int
+		expectSubstr  []string // substrings that should appear in changes
+	}{
+		{
+			"no changes",
+			map[string]string{"description": "Test", "status": "pending"},
+			map[string]string{"description": "Test", "status": "pending"},
+			0, nil,
+		},
+		{
+			"status change",
+			map[string]string{"status": "pending"},
+			map[string]string{"status": "completed"},
+			1, []string{"status: pending → completed"},
+		},
+		{
+			"field added",
+			map[string]string{"description": "Test"},
+			map[string]string{"description": "Test", "priority": "H"},
+			1, []string{"priority: (none) → H"},
+		},
+		{
+			"field removed",
+			map[string]string{"description": "Test", "priority": "H"},
+			map[string]string{"description": "Test"},
+			1, []string{"priority: H → (none)"},
+		},
+		{
+			"skips uuid and timestamps",
+			map[string]string{"uuid": "abc", "created": "123", "modified": "456", "status": "pending"},
+			map[string]string{"uuid": "def", "created": "789", "modified": "012", "status": "completed"},
+			1, []string{"status"},
+		},
+		{
+			"multiple changes",
+			map[string]string{"description": "Old", "status": "pending", "priority": "L"},
+			map[string]string{"description": "New", "status": "active", "priority": "H"},
+			3, nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			changes := diffFields(tt.prev, tt.curr)
+			if len(changes) != tt.expectChanges {
+				t.Errorf("got %d changes, want %d: %v", len(changes), tt.expectChanges, changes)
+			}
+			for _, substr := range tt.expectSubstr {
+				found := false
+				for _, c := range changes {
+					if strings.Contains(c, substr) {
+						found = true
+						break
+					}
+				}
+				if !found {
+					t.Errorf("expected change containing %q, got %v", substr, changes)
+				}
+			}
+		})
+	}
+}
+
+func TestFormatFieldValue(t *testing.T) {
+	tests := []struct {
+		name     string
+		key      string
+		value    string
+		expected string
+	}{
+		{"status passthrough", "status", "pending", "pending"},
+		{"description passthrough", "description", "Buy milk", "Buy milk"},
+		{"due as unix timestamp", "due", "1771977600", "2026-02-25"},
+		{"invalid timestamp", "due", "not-a-number", "not-a-number"},
+		{"scheduled as timestamp", "scheduled", "1771977600", "2026-02-25"},
+		{"start as timestamp", "start", "1771977600", "2026-02-25"},
+		{"end as timestamp", "end", "1771977600", "2026-02-25"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := formatFieldValue(tt.key, tt.value)
+			if result != tt.expected {
+				t.Errorf("formatFieldValue(%q, %q) = %q, want %q", tt.key, tt.value, result, tt.expected)
+			}
+		})
+	}
+}
+
+func TestFormatTaskHistory_Empty(t *testing.T) {
+	result := FormatTaskHistory(nil)
+	if result != "No history found.\n" {
+		t.Errorf("expected 'No history found.\\n', got %q", result)
+	}
+
+	result = FormatTaskHistory([]HistoryEntry{})
+	if result != "No history found.\n" {
+		t.Errorf("expected 'No history found.\\n', got %q", result)
+	}
+}
+
+func TestFormatTaskHistory_CreateEntry(t *testing.T) {
+	entries := []HistoryEntry{
+		{
+			ID:         1,
+			Timestamp:  time.Date(2026, 2, 18, 10, 0, 0, 0, time.UTC),
+			ChangeType: "create",
+			Data:       "description: Buy groceries\nstatus: pending\npriority: H\ntags: errand,shopping",
+		},
+	}
+
+	result := FormatTaskHistory(entries)
+
+	if !strings.Contains(result, "created") {
+		t.Error("expected 'created' in output")
+	}
+	if !strings.Contains(result, "Buy groceries") {
+		t.Error("expected description in output")
+	}
+	if !strings.Contains(result, "priority:H") {
+		t.Error("expected priority in output")
+	}
+	if !strings.Contains(result, "+errand") {
+		t.Error("expected +errand tag in output")
+	}
+	if !strings.Contains(result, "+shopping") {
+		t.Error("expected +shopping tag in output")
+	}
+}
+
+func TestFormatTaskHistory_CreateWithDefaultPriority(t *testing.T) {
+	entries := []HistoryEntry{
+		{
+			ID:         1,
+			Timestamp:  time.Date(2026, 2, 18, 10, 0, 0, 0, time.UTC),
+			ChangeType: "create",
+			Data:       "description: Simple task\nstatus: pending\npriority: D",
+		},
+	}
+
+	result := FormatTaskHistory(entries)
+
+	// Default priority "D" should not be shown
+	if strings.Contains(result, "priority") {
+		t.Errorf("default priority should not appear in output: %s", result)
+	}
+}
+
+func TestFormatTaskHistory_UpdateDiff(t *testing.T) {
+	entries := []HistoryEntry{
+		{
+			ID:         1,
+			Timestamp:  time.Date(2026, 2, 18, 10, 0, 0, 0, time.UTC),
+			ChangeType: "create",
+			Data:       "description: Buy groceries\nstatus: pending\npriority: D",
+		},
+		{
+			ID:         2,
+			Timestamp:  time.Date(2026, 2, 18, 11, 0, 0, 0, time.UTC),
+			ChangeType: "update",
+			Data:       "description: Buy groceries\nstatus: pending\npriority: H",
+		},
+	}
+
+	result := FormatTaskHistory(entries)
+
+	if !strings.Contains(result, "modified") {
+		t.Error("expected 'modified' in output for update with diff")
+	}
+	// Should show priority change
+	if !strings.Contains(result, "priority") {
+		t.Errorf("expected priority change in diff output: %s", result)
+	}
+}
+
+func TestFormatTaskHistory_DeleteEntry(t *testing.T) {
+	entries := []HistoryEntry{
+		{
+			ID:         1,
+			Timestamp:  time.Date(2026, 2, 18, 10, 0, 0, 0, time.UTC),
+			ChangeType: "create",
+			Data:       "description: Task\nstatus: pending",
+		},
+		{
+			ID:         2,
+			Timestamp:  time.Date(2026, 2, 18, 12, 0, 0, 0, time.UTC),
+			ChangeType: "delete",
+			Data:       "",
+		},
+	}
+
+	result := FormatTaskHistory(entries)
+	if !strings.Contains(result, "deleted") {
+		t.Error("expected 'deleted' in output")
+	}
+}
+
+func TestFormatTaskHistory_UpdateWithNoPrev(t *testing.T) {
+	// Update entry without a preceding create (edge case)
+	entries := []HistoryEntry{
+		{
+			ID:         1,
+			Timestamp:  time.Date(2026, 2, 18, 10, 0, 0, 0, time.UTC),
+			ChangeType: "update",
+			Data:       "description: Task\nstatus: completed",
+		},
+	}
+
+	result := FormatTaskHistory(entries)
+	if !strings.Contains(result, "updated") {
+		t.Errorf("expected 'updated' for update with no prev: %s", result)
+	}
+}
+
+func TestFormatTaskHistory_TimestampFormat(t *testing.T) {
+	entries := []HistoryEntry{
+		{
+			ID:         1,
+			Timestamp:  time.Date(2026, 2, 18, 14, 30, 0, 0, time.UTC),
+			ChangeType: "create",
+			Data:       "description: Test\nstatus: pending",
+		},
+	}
+
+	result := FormatTaskHistory(entries)
+	if !strings.Contains(result, "2026-02-18 14:30") {
+		t.Errorf("expected timestamp '2026-02-18 14:30' in output: %s", result)
+	}
+}
+
+func TestParseUnixString(t *testing.T) {
+	tests := []struct {
+		name    string
+		input   string
+		wantErr bool
+		year    int
+	}{
+		{"valid timestamp", "1771977600", false, 2026},
+		{"zero", "0", false, 1970},
+		{"invalid", "abc", true, 0},
+		{"empty", "", true, 0},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := parseUnixString(tt.input)
+			if tt.wantErr {
+				if err == nil {
+					t.Error("expected error but got none")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			if result.Year() != tt.year {
+				t.Errorf("year = %d, want %d", result.Year(), tt.year)
+			}
+		})
+	}
+}
diff --git a/opal-task/internal/engine/reldate_test.go b/opal-task/internal/engine/reldate_test.go
new file mode 100644
index 0000000..0911268
--- /dev/null
+++ b/opal-task/internal/engine/reldate_test.go
@@ -0,0 +1,214 @@
+package engine
+
+import (
+	"testing"
+	"time"
+)
+
+func TestFormatRelativeDate(t *testing.T) {
+	// Fix timeNow for deterministic tests
+	origTimeNow := timeNow
+	defer func() { timeNow = origTimeNow }()
+
+	// Wednesday, Feb 18, 2026 at 14:30 local time
+	now := time.Date(2026, 2, 18, 14, 30, 0, 0, time.Local)
+	timeNow = func() time.Time { return now }
+
+	tests := []struct {
+		name     string
+		input    time.Time
+		expected string
+	}{
+		// Core relative dates
+		{"today", time.Date(2026, 2, 18, 0, 0, 0, 0, time.Local), "today"},
+		{"today with time", time.Date(2026, 2, 18, 23, 59, 0, 0, time.Local), "today"},
+		{"tomorrow", time.Date(2026, 2, 19, 0, 0, 0, 0, time.Local), "tomorrow"},
+		{"yesterday", time.Date(2026, 2, 17, 0, 0, 0, 0, time.Local), "yesterday"},
+
+		// Near future
+		{"in 2d", time.Date(2026, 2, 20, 0, 0, 0, 0, time.Local), "in 2d"},
+		{"in 7d", time.Date(2026, 2, 25, 0, 0, 0, 0, time.Local), "in 7d"},
+		{"in 14d", time.Date(2026, 3, 4, 0, 0, 0, 0, time.Local), "in 14d"},
+
+		// Near past
+		{"2d ago", time.Date(2026, 2, 16, 0, 0, 0, 0, time.Local), "2d ago"},
+		{"7d ago", time.Date(2026, 2, 11, 0, 0, 0, 0, time.Local), "7d ago"},
+		{"14d ago", time.Date(2026, 2, 4, 0, 0, 0, 0, time.Local), "14d ago"},
+
+		// Beyond 14 days - same year
+		{"15d future", time.Date(2026, 3, 5, 0, 0, 0, 0, time.Local), "Mar 5"},
+		{"15d past", time.Date(2026, 2, 3, 0, 0, 0, 0, time.Local), "Feb 3"},
+
+		// Cross-year
+		{"next year", time.Date(2027, 6, 15, 0, 0, 0, 0, time.Local), "Jun 15 2027"},
+		{"last year", time.Date(2025, 12, 1, 0, 0, 0, 0, time.Local), "Dec 1 2025"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := FormatRelativeDate(tt.input)
+			if result != tt.expected {
+				t.Errorf("FormatRelativeDate(%v) = %q, want %q", tt.input, result, tt.expected)
+			}
+		})
+	}
+}
+
+func TestFormatRelativeDate_WeekdayPipeline(t *testing.T) {
+	// This test reproduces the reported bug:
+	// On Wednesday, "due:friday" should show "in 2d", not "tomorrow"
+	origTimeNow := timeNow
+	defer func() { timeNow = origTimeNow }()
+
+	// Wednesday, Feb 18, 2026
+	wednesday := time.Date(2026, 2, 18, 10, 0, 0, 0, time.Local)
+	timeNow = func() time.Time { return wednesday }
+
+	parser := NewDateParser(wednesday, time.Monday)
+
+	tests := []struct {
+		name        string
+		weekday     string
+		expectedRel string
+		expectedDay time.Weekday
+	}{
+		{"friday from wednesday", "friday", "in 2d", time.Friday},
+		{"fri from wednesday", "fri", "in 2d", time.Friday},
+		{"thursday from wednesday", "thu", "tomorrow", time.Thursday},
+		{"saturday from wednesday", "sat", "in 3d", time.Saturday},
+		{"sunday from wednesday", "sun", "in 4d", time.Sunday},
+		{"monday from wednesday", "mon", "in 5d", time.Monday},
+		{"tuesday from wednesday", "tue", "in 6d", time.Tuesday},
+		{"wednesday from wednesday", "wed", "in 7d", time.Wednesday},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			parsed, err := parser.ParseDate(tt.weekday)
+			if err != nil {
+				t.Fatalf("ParseDate(%q) error: %v", tt.weekday, err)
+			}
+
+			// Verify correct weekday
+			if parsed.Weekday() != tt.expectedDay {
+				t.Errorf("ParseDate(%q) weekday = %v, want %v", tt.weekday, parsed.Weekday(), tt.expectedDay)
+			}
+
+			// Verify relative display
+			rel := FormatRelativeDate(parsed)
+			if rel != tt.expectedRel {
+				t.Errorf("FormatRelativeDate(ParseDate(%q)) = %q, want %q (parsed date: %v)",
+					tt.weekday, rel, tt.expectedRel, parsed)
+			}
+		})
+	}
+}
+
+func TestFormatRelativeDate_AllWeekdaysFromAllDays(t *testing.T) {
+	// Exhaustive: parse every weekday name from every starting day of the week
+	origTimeNow := timeNow
+	defer func() { timeNow = origTimeNow }()
+
+	// Week starting Monday Feb 16 2026
+	weekStart := time.Date(2026, 2, 16, 12, 0, 0, 0, time.Local) // Monday
+
+	weekdays := []string{"mon", "tue", "wed", "thu", "fri", "sat", "sun"}
+	targetWeekdays := []time.Weekday{
+		time.Monday, time.Tuesday, time.Wednesday, time.Thursday,
+		time.Friday, time.Saturday, time.Sunday,
+	}
+
+	for fromOffset := 0; fromOffset < 7; fromOffset++ {
+		fromDate := weekStart.AddDate(0, 0, fromOffset)
+		fromName := fromDate.Weekday().String()
+
+		timeNow = func() time.Time { return fromDate }
+		parser := NewDateParser(fromDate, time.Monday)
+
+		for i, dayName := range weekdays {
+			t.Run(fromName+"_to_"+dayName, func(t *testing.T) {
+				parsed, err := parser.ParseDate(dayName)
+				if err != nil {
+					t.Fatalf("ParseDate(%q) from %s: %v", dayName, fromName, err)
+				}
+
+				// Must be the correct weekday
+				if parsed.Weekday() != targetWeekdays[i] {
+					t.Errorf("wrong weekday: got %v, want %v", parsed.Weekday(), targetWeekdays[i])
+				}
+
+				// Must be in the future (1-7 days from now)
+				diff := parsed.Sub(time.Date(fromDate.Year(), fromDate.Month(), fromDate.Day(), 0, 0, 0, 0, time.Local))
+				days := int(diff.Hours() / 24)
+				if days < 1 || days > 7 {
+					t.Errorf("ParseDate(%q) from %s: expected 1-7 days ahead, got %d (parsed: %v)",
+						dayName, fromName, days, parsed)
+				}
+
+				// FormatRelativeDate must match the days offset
+				rel := FormatRelativeDate(parsed)
+				if days == 1 && rel != "tomorrow" {
+					t.Errorf("1 day ahead should be 'tomorrow', got %q", rel)
+				}
+				if days > 1 && days <= 7 {
+					expected := "in " + string(rune('0'+days)) + "d"
+					if days >= 10 {
+						// won't happen for weekdays (max 7)
+					}
+					if rel != expected {
+						t.Errorf("from %s, %q: %d days ahead, got rel=%q, want %q",
+							fromName, dayName, days, rel, expected)
+					}
+				}
+			})
+		}
+	}
+}
+
+func TestFormatRelativeDate_TimezoneConsistency(t *testing.T) {
+	// Verify that dates in UTC vs Local don't produce wrong relative strings
+	origTimeNow := timeNow
+	defer func() { timeNow = origTimeNow }()
+
+	now := time.Date(2026, 2, 18, 14, 0, 0, 0, time.Local)
+	timeNow = func() time.Time { return now }
+
+	// A date 2 days from now, but in UTC
+	targetUTC := time.Date(2026, 2, 20, 0, 0, 0, 0, time.UTC)
+	// Same date in Local
+	targetLocal := time.Date(2026, 2, 20, 0, 0, 0, 0, time.Local)
+
+	relUTC := FormatRelativeDate(targetUTC)
+	relLocal := FormatRelativeDate(targetLocal)
+
+	// Both should show "in 2d" - if UTC shows something different, that's a bug
+	if relLocal != "in 2d" {
+		t.Errorf("Local target: expected 'in 2d', got %q", relLocal)
+	}
+
+	// Note: UTC target may differ depending on system timezone.
+	// This test documents the behavior.
+	t.Logf("Local timezone: now=%v", now)
+	t.Logf("UTC target relative: %q, Local target relative: %q", relUTC, relLocal)
+
+	if relUTC != relLocal {
+		t.Logf("WARNING: timezone mismatch detected — UTC shows %q vs Local shows %q", relUTC, relLocal)
+		t.Logf("This could explain the 'due:friday shows tomorrow' bug if dates are stored/loaded in wrong timezone")
+	}
+}
+
+func TestFormatDateWithRelative(t *testing.T) {
+	origTimeNow := timeNow
+	defer func() { timeNow = origTimeNow }()
+
+	now := time.Date(2026, 2, 18, 14, 0, 0, 0, time.Local)
+	timeNow = func() time.Time { return now }
+
+	input := time.Date(2026, 2, 20, 15, 30, 0, 0, time.Local)
+	result := FormatDateWithRelative(input)
+
+	// Should contain both absolute and relative
+	if result != "2026-02-20 15:30 (in 2d)" {
+		t.Errorf("FormatDateWithRelative = %q, want %q", result, "2026-02-20 15:30 (in 2d)")
+	}
+}
diff --git a/opal-task/internal/engine/undo_test.go b/opal-task/internal/engine/undo_test.go
new file mode 100644
index 0000000..9f8a70d
--- /dev/null
+++ b/opal-task/internal/engine/undo_test.go
@@ -0,0 +1,275 @@
+package engine
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestRecordUndo_And_PopUndo_Add(t *testing.T) {
+	// Create a task, record undo, then pop undo — should hard-delete the task
+	task, err := CreateTask("Undo add test")
+	if err != nil {
+		t.Fatalf("CreateTask: %v", err)
+	}
+
+	if err := RecordUndo("add", task.UUID); err != nil {
+		t.Fatalf("RecordUndo: %v", err)
+	}
+
+	desc, err := PopUndo()
+	if err != nil {
+		t.Fatalf("PopUndo: %v", err)
+	}
+
+	if !strings.Contains(desc, "Undo") || !strings.Contains(desc, "add") {
+		t.Errorf("unexpected undo description: %s", desc)
+	}
+
+	// Task should be gone
+	_, err = GetTask(task.UUID)
+	if err == nil {
+		t.Error("task should have been hard-deleted after undo add")
+	}
+}
+
+func TestRecordUndo_And_PopUndo_Done(t *testing.T) {
+	task, err := CreateTask("Undo done test")
+	if err != nil {
+		t.Fatalf("CreateTask: %v", err)
+	}
+	defer func() { task.Delete(true) }()
+
+	// Record undo for the initial creation (so we have a prior change_log entry)
+	// Note: the change_log trigger auto-records on creation, so we just need to
+	// complete and record undo for the completion.
+
+	// Complete the task
+	task.Status = StatusCompleted
+	now := timeNow()
+	task.End = &now
+	if err := task.Save(); err != nil {
+		t.Fatalf("Save completed: %v", err)
+	}
+
+	if err := RecordUndo("done", task.UUID); err != nil {
+		t.Fatalf("RecordUndo: %v", err)
+	}
+
+	// Undo should restore to pending
+	desc, err := PopUndo()
+	if err != nil {
+		t.Fatalf("PopUndo: %v", err)
+	}
+
+	if !strings.Contains(desc, "done") {
+		t.Errorf("expected 'done' in description: %s", desc)
+	}
+
+	// Reload and check status
+	reloaded, err := GetTask(task.UUID)
+	if err != nil {
+		t.Fatalf("GetTask after undo: %v", err)
+	}
+	if reloaded.Status != StatusPending {
+		t.Errorf("status after undo done = %d, want %d (pending)", reloaded.Status, StatusPending)
+	}
+	if reloaded.End != nil {
+		t.Error("End should be nil after undo done")
+	}
+}
+
+func TestRecordUndo_And_PopUndo_Modify(t *testing.T) {
+	task, err := CreateTask("Undo modify test")
+	if err != nil {
+		t.Fatalf("CreateTask: %v", err)
+	}
+	defer func() { task.Delete(true) }()
+
+	// Modify the task
+	task.Description = "Modified description"
+	task.Priority = PriorityHigh
+	if err := task.Save(); err != nil {
+		t.Fatalf("Save modified: %v", err)
+	}
+
+	if err := RecordUndo("modify", task.UUID); err != nil {
+		t.Fatalf("RecordUndo: %v", err)
+	}
+
+	// Undo should restore original description and priority
+	_, err = PopUndo()
+	if err != nil {
+		t.Fatalf("PopUndo: %v", err)
+	}
+
+	reloaded, err := GetTask(task.UUID)
+	if err != nil {
+		t.Fatalf("GetTask after undo: %v", err)
+	}
+	if reloaded.Description != "Undo modify test" {
+		t.Errorf("description after undo = %q, want %q", reloaded.Description, "Undo modify test")
+	}
+	if reloaded.Priority != PriorityDefault {
+		t.Errorf("priority after undo = %d, want %d (default)", reloaded.Priority, PriorityDefault)
+	}
+}
+
+func TestPopUndo_EmptyStack(t *testing.T) {
+	// Clear the undo stack
+	db := GetDB()
+	db.Exec("DELETE FROM undo_stack")
+
+	_, err := PopUndo()
+	if err == nil {
+		t.Error("PopUndo on empty stack should return error")
+	}
+	if !strings.Contains(err.Error(), "nothing to undo") {
+		t.Errorf("expected 'nothing to undo' error, got: %v", err)
+	}
+}
+
+func TestUndoStackEviction(t *testing.T) {
+	// Clear existing undo entries
+	db := GetDB()
+	db.Exec("DELETE FROM undo_stack")
+
+	// Create 12 tasks and record undo for each
+	for i := 0; i < 12; i++ {
+		task, err := CreateTask("Eviction test task")
+		if err != nil {
+			t.Fatalf("CreateTask %d: %v", i, err)
+		}
+		if err := RecordUndo("add", task.UUID); err != nil {
+			t.Fatalf("RecordUndo %d: %v", i, err)
+		}
+	}
+
+	// Stack should be capped at 10
+	var count int
+	if err := db.QueryRow("SELECT COUNT(*) FROM undo_stack").Scan(&count); err != nil {
+		t.Fatalf("count query: %v", err)
+	}
+	if count != 10 {
+		t.Errorf("undo stack count = %d, want 10 (limit)", count)
+	}
+}
+
+func TestApplyChangeLogData(t *testing.T) {
+	task, err := CreateTask("Apply changelog test")
+	if err != nil {
+		t.Fatalf("CreateTask: %v", err)
+	}
+	defer func() { task.Delete(true) }()
+
+	// Apply changelog data that sets various fields
+	due := time.Date(2026, 3, 1, 0, 0, 0, 0, time.UTC)
+	data := "description: Changed description\nstatus: completed\npriority: H\nproject: work\ndue: " +
+		strings.TrimSpace(time.Unix(due.Unix(), 0).Format("")) + "\n"
+
+	// Construct proper data string
+	data = "description: Changed description\nstatus: completed\npriority: H\nproject: work"
+
+	if err := applyChangeLogData(task, data); err != nil {
+		t.Fatalf("applyChangeLogData: %v", err)
+	}
+
+	if task.Description != "Changed description" {
+		t.Errorf("description = %q, want %q", task.Description, "Changed description")
+	}
+	if task.Status != StatusCompleted {
+		t.Errorf("status = %d, want %d", task.Status, StatusCompleted)
+	}
+	if task.Priority != PriorityHigh {
+		t.Errorf("priority = %d, want %d", task.Priority, PriorityHigh)
+	}
+	if task.Project == nil || *task.Project != "work" {
+		t.Error("project should be 'work'")
+	}
+}
+
+func TestApplyChangeLogData_ClearsAbsentFields(t *testing.T) {
+	task, err := CreateTask("Clear fields test")
+	if err != nil {
+		t.Fatalf("CreateTask: %v", err)
+	}
+	defer func() { task.Delete(true) }()
+
+	// Set some fields first
+	proj := "work"
+	task.Project = &proj
+	now := timeNow()
+	task.Due = &now
+	task.Start = &now
+
+	// Apply data without project, due, or start — they should be cleared
+	data := "description: Clear fields test\nstatus: pending"
+	if err := applyChangeLogData(task, data); err != nil {
+		t.Fatalf("applyChangeLogData: %v", err)
+	}
+
+	if task.Project != nil {
+		t.Error("project should be nil after applying data without project")
+	}
+	if task.Due != nil {
+		t.Error("due should be nil after applying data without due")
+	}
+	if task.Start != nil {
+		t.Error("start should be nil after applying data without start")
+	}
+}
+
+func TestReconcileTagsFromChangeLog(t *testing.T) {
+	task, err := CreateTask("Tag reconcile test")
+	if err != nil {
+		t.Fatalf("CreateTask: %v", err)
+	}
+	defer func() { task.Delete(true) }()
+
+	// Set current tags
+	task.AddTag("keep")
+	task.AddTag("remove")
+
+	// Reconcile with data that has "keep" and "add" but not "remove"
+	data := "tags: keep,add"
+	if err := reconcileTagsFromChangeLog(task, data); err != nil {
+		t.Fatalf("reconcileTagsFromChangeLog: %v", err)
+	}
+
+	tags, _ := task.GetTags()
+	tagSet := make(map[string]bool)
+	for _, tag := range tags {
+		tagSet[tag] = true
+	}
+
+	if !tagSet["keep"] {
+		t.Error("tag 'keep' should still be present")
+	}
+	if !tagSet["add"] {
+		t.Error("tag 'add' should have been added")
+	}
+	if tagSet["remove"] {
+		t.Error("tag 'remove' should have been removed")
+	}
+}
+
+func TestReconcileTagsFromChangeLog_NoTags(t *testing.T) {
+	task, err := CreateTask("No tags reconcile test")
+	if err != nil {
+		t.Fatalf("CreateTask: %v", err)
+	}
+	defer func() { task.Delete(true) }()
+
+	task.AddTag("should-be-removed")
+
+	// Data with no tags line — all tags should be removed
+	data := "description: No tags reconcile test\nstatus: pending"
+	if err := reconcileTagsFromChangeLog(task, data); err != nil {
+		t.Fatalf("reconcileTagsFromChangeLog: %v", err)
+	}
+
+	tags, _ := task.GetTags()
+	if len(tags) != 0 {
+		t.Errorf("expected 0 tags after reconcile with no tags, got %v", tags)
+	}
+}