diff --git a/automations_models.go b/automations_models.go
index fc7f260..e7cda56 100644
--- a/automations_models.go
+++ b/automations_models.go
@@ -14,6 +14,11 @@ type AutomationRuleUpdateRequest struct {
 	Enabled *bool `json:"enabled,omitempty" toon:"enabled,omitempty"`
 	// Run cadence. Supports 4 fields (`hour day month weekday`, minute defaults to 0) and 5 fields (`minute hour day month weekday`).
 	CronExpr *string `json:"cron_expr,omitempty" toon:"cron_expr,omitempty"`
+	// IANA timezone `cron_expr` is evaluated in. The server must be able to load
+	// the name; an invalid value is rejected. Nil leaves the stored timezone
+	// unchanged, including a legacy empty string. An explicit empty string is
+	// stored as UTC, not reset to the account default.
+	Timezone *string `json:"timezone,omitempty" toon:"timezone,omitempty"`
 	// Whether the schedule trigger is enabled.
 	ScheduleTriggerEnabled *bool `json:"schedule_trigger_enabled,omitempty" toon:"schedule_trigger_enabled,omitempty"`
 	// New task prompt.
diff --git a/automations_models_test.go b/automations_models_test.go
new file mode 100644
index 0000000..15f630d
--- /dev/null
+++ b/automations_models_test.go
@@ -0,0 +1,39 @@
+package flashduty
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+func TestAutomationRuleUpdateRequestTimezone(t *testing.T) {
+	omitted, err := json.Marshal(&AutomationRuleUpdateRequest{RuleID: "arule_1"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(string(omitted), "timezone") {
+		t.Fatalf("nil timezone must be omitted, got %s", omitted)
+	}
+
+	empty, err := json.Marshal(&AutomationRuleUpdateRequest{
+		RuleID:   "arule_1",
+		Timezone: String(""),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(string(empty), `"timezone":""`) {
+		t.Fatalf("empty timezone must be sent, got %s", empty)
+	}
+
+	named, err := json.Marshal(&AutomationRuleUpdateRequest{
+		RuleID:   "arule_1",
+		Timezone: String("Asia/Shanghai"),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(string(named), `"timezone":"Asia/Shanghai"`) {
+		t.Fatalf("named timezone must be sent, got %s", named)
+	}
+}