diff --git a/internal/cmd/time_helpers.go b/internal/cmd/time_helpers.go
index cf6aa75d..0842cc0d 100644
--- a/internal/cmd/time_helpers.go
+++ b/internal/cmd/time_helpers.go
@@ -3,6 +3,7 @@ package cmd
 import (
 	"context"
 	"fmt"
+	"log/slog"
 	"strings"
 	"time"
 
@@ -52,14 +53,19 @@ func getCalendarLocation(ctx context.Context, svc *calendar.Service, calendarID
 }
 
 // getUserTimezone fetches the timezone from the user's primary calendar.
+// When no primary calendar exists (e.g. pure service-account mode), it
+// falls back to UTC so that calendar commands remain functional.
 func getUserTimezone(ctx context.Context, svc *calendar.Service) (*time.Location, error) {
 	cal, err := svc.CalendarList.Get("primary").Context(ctx).Do()
 	if err != nil {
+		if isNotFoundAPIError(err) {
+			slog.Warn("primary calendar not found, falling back to UTC (expected in pure SA mode)")
+			return time.UTC, nil
+		}
 		return nil, fmt.Errorf("failed to get primary calendar: %w", err)
 	}
 
 	if cal.TimeZone == "" {
-		// Fall back to UTC if no timezone set
 		return time.UTC, nil
 	}
 
diff --git a/internal/cmd/time_helpers_sa_test.go b/internal/cmd/time_helpers_sa_test.go
new file mode 100644
index 00000000..1c7e6d29
--- /dev/null
+++ b/internal/cmd/time_helpers_sa_test.go
@@ -0,0 +1,64 @@
+package cmd
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"google.golang.org/api/calendar/v3"
+	"google.golang.org/api/option"
+)
+
+// newCalendarServicePrimaryNotFound creates a calendar service whose
+// CalendarList.Get("primary") endpoint returns 404, simulating pure
+// service-account mode where no primary calendar exists.
+func newCalendarServicePrimaryNotFound(t *testing.T) *calendar.Service {
+	t.Helper()
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// All calendarList requests return 404.
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusNotFound)
+		_, _ = w.Write([]byte(`{"error":{"code":404,"message":"Not Found","errors":[{"message":"Not Found","domain":"global","reason":"notFound"}]}}`))
+	}))
+	t.Cleanup(srv.Close)
+
+	svc, err := calendar.NewService(context.Background(),
+		option.WithoutAuthentication(),
+		option.WithHTTPClient(srv.Client()),
+		option.WithEndpoint(srv.URL+"/"),
+	)
+	if err != nil {
+		t.Fatalf("NewService: %v", err)
+	}
+	return svc
+}
+
+func TestGetUserTimezone_PrimaryNotFound_FallsBackToUTC(t *testing.T) {
+	svc := newCalendarServicePrimaryNotFound(t)
+
+	loc, err := getUserTimezone(context.Background(), svc)
+	if err != nil {
+		t.Fatalf("getUserTimezone returned error: %v", err)
+	}
+	if loc != time.UTC {
+		t.Fatalf("expected UTC fallback, got %v", loc)
+	}
+}
+
+func TestResolveTimeRange_PrimaryNotFound_Succeeds(t *testing.T) {
+	svc := newCalendarServicePrimaryNotFound(t)
+
+	tr, err := ResolveTimeRange(context.Background(), svc, TimeRangeFlags{})
+	if err != nil {
+		t.Fatalf("ResolveTimeRange returned error: %v", err)
+	}
+	if tr.Location != time.UTC {
+		t.Fatalf("expected UTC location, got %v", tr.Location)
+	}
+	if tr.From.IsZero() || tr.To.IsZero() {
+		t.Fatal("expected non-zero time range")
+	}
+}