diff --git a/internal/services/automation/automation_schedule_resource.go b/internal/services/automation/automation_schedule_resource.go
index e91a83971f30..906d3c432e79 100644
--- a/internal/services/automation/automation_schedule_resource.go
+++ b/internal/services/automation/automation_schedule_resource.go
@@ -86,7 +86,7 @@ func resourceAutomationSchedule() *pluginsdk.Resource {
 				Type:             pluginsdk.TypeString,
 				Optional:         true,
 				Computed:         true,
-				DiffSuppressFunc: suppress.RFC3339Time,
+				DiffSuppressFunc: suppress.RFC3339MinuteTime,
 				ValidateFunc:     validation.IsRFC3339Time,
 				// defaults to now + 7 minutes in create function if not set
 			},
@@ -95,7 +95,7 @@ func resourceAutomationSchedule() *pluginsdk.Resource {
 				Type:             pluginsdk.TypeString,
 				Optional:         true,
 				Computed:         true, // same as start time when OneTime, ridiculous value when recurring: "9999-12-31T15:59:00-08:00"
-				DiffSuppressFunc: suppress.CaseDifference,
+				DiffSuppressFunc: suppress.RFC3339MinuteTime,
 				ValidateFunc:     validation.IsRFC3339Time,
 			},
 
@@ -262,8 +262,7 @@ func resourceAutomationScheduleCreateUpdate(d *pluginsdk.ResourceData, meta inte
 	}
 
 	if v, ok := d.GetOk("expiry_time"); ok {
-		t, _ := time.Parse(time.RFC3339, v.(string)) // should be validated by the schema
-		parameters.Properties.SetExpiryTimeAsTime(t.In(loc))
+		parameters.Properties.ExpiryTime = pointer.To(v.(string))
 	}
 
 	// only pay attention to interval if frequency is not OneTime, and default it to 1 if not set
@@ -324,12 +323,7 @@ func resourceAutomationScheduleRead(d *pluginsdk.ResourceData, meta interface{})
 				return err
 			}
 			d.Set("start_time", startTime.Format(time.RFC3339))
-
-			expiryTime, err := props.GetExpiryTimeAsTime()
-			if err != nil {
-				return err
-			}
-			d.Set("expiry_time", expiryTime.Format(time.RFC3339))
+			d.Set("expiry_time", pointer.From(props.ExpiryTime))
 
 			if v := props.Interval; v != nil {
 				d.Set("interval", v)
diff --git a/internal/services/automation/automation_schedule_resource_test.go b/internal/services/automation/automation_schedule_resource_test.go
index 4bd3d91698ad..8040780e30cd 100644
--- a/internal/services/automation/automation_schedule_resource_test.go
+++ b/internal/services/automation/automation_schedule_resource_test.go
@@ -31,6 +31,29 @@ func TestAccAutomationSchedule_oneTime_basic(t *testing.T) {
 	})
 }
 
+// test for: https://github.com/hashicorp/terraform-provider-azurerm/issues/21854
+func TestAccAutomationSchedule_expiryTimeOfEuropeTimeZone(t *testing.T) {
+	data := acceptance.BuildTestData(t, "azurerm_automation_schedule", "test")
+	r := AutomationScheduleResource{}
+
+	data.ResourceTest(t, r, []acceptance.TestStep{
+		{
+			Config: r.expiryTimeOfEuropeTimeZone(data, "foo"),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+			),
+		},
+		data.ImportStep(),
+		{
+			Config: r.expiryTimeOfEuropeTimeZone(data, "bar"),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+			),
+		},
+		data.ImportStep(),
+	})
+}
+
 func TestAccAutomationSchedule_requiresImport(t *testing.T) {
 	data := acceptance.BuildTestData(t, "azurerm_automation_schedule", "test")
 	r := AutomationScheduleResource{}
@@ -245,6 +268,24 @@ resource "azurerm_automation_schedule" "test" {
 `, AutomationScheduleResource{}.template(data), data.RandomInteger)
 }
 
+func (a AutomationScheduleResource) expiryTimeOfEuropeTimeZone(data acceptance.TestData, desc string) string {
+	return fmt.Sprintf(`
+%s
+
+resource "azurerm_automation_schedule" "test" {
+  name                    = "acctestAS-%d"
+  resource_group_name     = azurerm_resource_group.test.name
+  automation_account_name = azurerm_automation_account.test.name
+  frequency               = "Week"
+  interval                = 1
+  timezone                = "Europe/Amsterdam"
+  start_time              = "2026-04-15T18:01:15+02:00"
+  description             = "%s"
+  week_days               = ["Monday"]
+}
+`, a.template(data), data.RandomInteger, desc)
+}
+
 func (AutomationScheduleResource) requiresImport(data acceptance.TestData) string {
 	return fmt.Sprintf(`
 %s