diff --git a/internal/database/audit.go b/internal/database/audit.go
index 7853ddf5..a4bfe6cb 100644
--- a/internal/database/audit.go
+++ b/internal/database/audit.go
@@ -69,12 +69,12 @@ func buildAuditLogsWhere(filter ListAuditLogsFilter) (string, []interface{}) {
 		args = append(args, filter.ResourceID)
 	}
 	if filter.Since != nil {
-		conditions = append(conditions, "created_at >= ?")
-		args = append(args, *filter.Since)
+		conditions = append(conditions, sqliteEpochGE("created_at", ">="))
+		args = append(args, formatSQLiteUTC(*filter.Since))
 	}
 	if filter.Until != nil {
-		conditions = append(conditions, "created_at <= ?")
-		args = append(args, *filter.Until)
+		conditions = append(conditions, sqliteEpochGE("created_at", "<="))
+		args = append(args, formatSQLiteUTC(*filter.Until))
 	}
 	if q := strings.TrimSpace(filter.Query); q != "" {
 		like := "%" + q + "%"
@@ -93,7 +93,9 @@ func (db *DB) AppendAuditLog(row *AuditLog) error {
 		return errors.New("audit id is required")
 	}
 	if row.CreatedAt.IsZero() {
-		row.CreatedAt = time.Now()
+		row.CreatedAt = time.Now().UTC()
+	} else {
+		row.CreatedAt = row.CreatedAt.UTC()
 	}
 	if strings.TrimSpace(row.Level) == "" {
 		row.Level = "info"
@@ -111,7 +113,7 @@ func (db *DB) AppendAuditLog(row *AuditLog) error {
 		) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
 	`
 	_, err := db.Exec(query,
-		row.ID, row.CreatedAt, row.Level, row.Category, row.Action, row.Result,
+		row.ID, formatSQLiteUTC(row.CreatedAt), row.Level, row.Category, row.Action, row.Result,
 		row.Actor, row.SessionHint, row.ClientIP, row.UserAgent,
 		row.ResourceType, row.ResourceID, row.Message, detailJSON,
 	)
@@ -202,7 +204,7 @@ func (db *DB) ListAuditLogs(filter ListAuditLogsFilter) ([]*AuditLog, error) {
 
 // DeleteAuditLogsBefore removes rows older than cutoff.
 func (db *DB) DeleteAuditLogsBefore(cutoff time.Time) (int64, error) {
-	res, err := db.Exec(`DELETE FROM audit_logs WHERE created_at < ?`, cutoff)
+	res, err := db.Exec(`DELETE FROM audit_logs WHERE `+sqliteEpochGE("created_at", "<"), formatSQLiteUTC(cutoff))
 	if err != nil {
 		return 0, err
 	}
diff --git a/internal/database/audit_time_test.go b/internal/database/audit_time_test.go
new file mode 100644
index 00000000..f4d36026
--- /dev/null
+++ b/internal/database/audit_time_test.go
@@ -0,0 +1,62 @@
+package database
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"go.uber.org/zap"
+)
+
+func TestBuildAuditLogsWhere_timeFilterSQL(t *testing.T) {
+	since := time.Date(2026, 6, 16, 17, 2, 0, 0, time.UTC)
+	until := time.Date(2026, 6, 17, 3, 3, 0, 0, time.UTC)
+	where, args := buildAuditLogsWhere(ListAuditLogsFilter{Since: &since, Until: &until})
+	if !strings.Contains(where, "strftime('%s', created_at) >=") {
+		t.Fatalf("expected epoch comparison for since, got %q", where)
+	}
+	if !strings.Contains(where, "strftime('%s', created_at) <=") {
+		t.Fatalf("expected epoch comparison for until, got %q", where)
+	}
+	if len(args) != 2 {
+		t.Fatalf("expected 2 time args, got %d", len(args))
+	}
+	for i, arg := range args {
+		s, ok := arg.(string)
+		if !ok || s == "" {
+			t.Fatalf("arg %d: want non-empty UTC RFC3339 string, got %v", i, arg)
+		}
+	}
+}
+
+func TestListAuditLogs_timeFilterMixedStorageFormats(t *testing.T) {
+	root, err := os.Getwd()
+	if err != nil {
+		t.Skip(err)
+	}
+	dbPath := filepath.Join(root, "..", "..", "data", "conversations.db")
+	if _, err := os.Stat(dbPath); err != nil {
+		t.Skip("conversations.db not found")
+	}
+	db, err := NewDB(dbPath, zap.NewNop())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	since, _ := ParseRFC3339Time("2026-06-16T17:02:00Z")
+	until, _ := ParseRFC3339Time("2026-06-17T03:03:00Z")
+	filter := ListAuditLogsFilter{Since: &since, Until: &until, Limit: 50}
+	logs, err := db.ListAuditLogs(filter)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, row := range logs {
+		at := row.CreatedAt.UTC()
+		if at.Before(since) || at.After(until) {
+			t.Fatalf("log %s at %s outside [%s, %s]", row.ID, at, since, until)
+		}
+	}
+}
diff --git a/internal/database/sqltime.go b/internal/database/sqltime.go
new file mode 100644
index 00000000..8089e44c
--- /dev/null
+++ b/internal/database/sqltime.go
@@ -0,0 +1,33 @@
+package database
+
+import (
+	"errors"
+	"strings"
+	"time"
+)
+
+// formatSQLiteUTC stores instants as UTC RFC3339 for consistent SQLite reads/writes.
+func formatSQLiteUTC(t time.Time) string {
+	return t.UTC().Format(time.RFC3339Nano)
+}
+
+// sqliteEpochGE returns SQL comparing column to param as Unix seconds (timezone-safe).
+func sqliteEpochGE(column, op string) string {
+	return "strftime('%s', " + column + ") " + op + " strftime('%s', ?)"
+}
+
+// ParseRFC3339Time parses API/query timestamps (RFC3339 or RFC3339Nano).
+func ParseRFC3339Time(value string) (time.Time, error) {
+	value = strings.TrimSpace(value)
+	if value == "" {
+		return time.Time{}, errors.New("empty time value")
+	}
+	if t, err := time.Parse(time.RFC3339Nano, value); err == nil {
+		return t.UTC(), nil
+	}
+	t, err := time.Parse(time.RFC3339, value)
+	if err != nil {
+		return time.Time{}, err
+	}
+	return t.UTC(), nil
+}