diff --git a/temba/triggers/views.py b/temba/triggers/views.py
index 2bd73ef83ce..28c2ea501d5 100644
--- a/temba/triggers/views.py
+++ b/temba/triggers/views.py
@@ -358,6 +358,7 @@ class BaseLargeSendForm(forms.ModelForm):
         (45, _("45 minutes")),
         (60, _("1 hour")),
     )
+    CHUNK_MAX_LIMIT = 500
 
     batch_interval = forms.ChoiceField(
         choices=BATCH_INTERVAL,
@@ -366,12 +367,14 @@ class BaseLargeSendForm(forms.ModelForm):
         required=True,
         widget=SelectWidget(),
     )
+
     flow = TembaChoiceField(
         Flow.objects.none(),
         label=_("Flow"),
         required=True,
         widget=SelectWidget(attrs={"placeholder": _("Select a flow"), "searchable": True}),
     )
+
     groups = TembaMultipleChoiceField(
         queryset=ContactGroup.user_groups.none(),
         label=_("Groups"),
@@ -381,15 +384,18 @@ class BaseLargeSendForm(forms.ModelForm):
             attrs={"icons": True, "placeholder": _("Select contact groups"), "searchable": True}
         ),
     )
+
     start_time = forms.DateTimeField(
         required=True,
         label=_("Start Time for Send"),
         widget=InputWidget(attrs={"datetimepicker": True, "placeholder": _("Select a date and time")}),
     )
+
     chunk_size = forms.IntegerField(
         label=_("Chunks"),
-        help_text=_("I want to split the message to this many pieces"),
-        widget=InputWidget(attrs={"type": "number", "placeholder": _("Enter chunk size")}),
+        max_value=CHUNK_MAX_LIMIT,
+        help_text=_("I want to split the message to this many pieces. Max: 500"),
+        widget=InputWidget(attrs={"type": "number", "max": CHUNK_MAX_LIMIT, "placeholder": _("Enter chunk size")}),
     )
 
     limit_time = forms.BooleanField(required=False, label=_("Limit to business hours"), help_text=_("9 AM to 5 PM"))
@@ -414,9 +420,14 @@ class LargeSendMixin:
 
     @classmethod
     def get_new_time(cls, input_time, hour, add_to_day=0):
-        input_time = datetime.datetime(
-            year=input_time.year, month=input_time.month, day=input_time.day + add_to_day, hour=hour
-        )
+        try:
+            input_time = datetime.datetime(
+                year=input_time.year, month=input_time.month, day=input_time.day + add_to_day, hour=hour
+            )
+        except ValueError:
+            input_time = datetime.datetime(
+                year=input_time.year, month=input_time.month, day=input_time.day, hour=hour
+            ) + timedelta(days=add_to_day)
         return timezone.make_aware(input_time)
 
     def derive_start_time(self, start_time, limit_time):
diff --git a/templates/triggers/trigger_create_large_send.haml b/templates/triggers/trigger_create_large_send.haml
index be13dda8ab9..80258cf9d50 100644
--- a/templates/triggers/trigger_create_large_send.haml
+++ b/templates/triggers/trigger_create_large_send.haml
@@ -91,6 +91,12 @@
         groupFields.forEach(elem => groupList.push(Number(elem.value)));
 
         if (startTime && groupList.length > 0 && intervalValue && chunkSizeValue) {
+          if (chunkSizeValue > 500) {
+            showAlertMessage("Chunks should be max of 500", "red");
+            recreatePrimaryButton(true);
+            return
+          }
+
           const formData = new FormData();
           formData.append('groups', groupList);
           formData.append('start_time', startTime);
@@ -100,24 +106,54 @@
           const formOption = {
             method: 'POST',
             body: formData,
+            signal: AbortSignal.timeout(30000),
             headers: {
               'X-Requested-With': 'XMLHttpRequest',
               'X-CSRFToken': getCookie('csrftoken')
             }
           }
+          showAlertMessage("Calculating groups...", "black");
+          recreatePrimaryButton(true);
           fetch('{% url "triggers.trigger_large_send_schedule_summary" %}', formOption)
             .then((response) => response.json())
             .then((response) => {
               toggleScheduleList(response);
+              recreatePrimaryButton(false);
+            }).catch((error) => {
+              console.log("[trigger_large_send_schedule_summary]", error)
+              showAlertMessage("Unable to process the summary, please try again.", "red")
             });
         }
-      }, 100);
+      }, 500);
+    }
+
+    function recreatePrimaryButton(disable) {
+      const { dialogFooter } = getFormElements();
+      const currentSubmit = dialogFooter.querySelector('temba-button');
+      let options = { name: 'Create', onclick: showConfirmation, primary: true };
+      if (disable) {
+        options['disabled'] = true;
+      }
+      const submitButton = createButton(options);
+      try {
+        if (currentSubmit) {
+          dialogFooter.removeChild(currentSubmit);
+          dialogFooter.prepend(submitButton);
+        }
+      } catch (e) {}
     }
 
     function chunkBy(number, n) {
       return new Array(Math.floor(number / n)).fill(n).concat(number % n)
     }
 
+    function showAlertMessage(msg, color) {
+      const { modaxBody } = getFormElements();
+      const scheduleListPreview = modaxBody.querySelector('.schedule-list-preview');
+      scheduleListPreview.innerHTML = `<p style="color: ${color}">${msg}</p>`;
+      scheduleListPreview.classList.remove('hidden');
+    }
+
     function toggleScheduleList(response) {
       const { modaxBody } = getFormElements();
       const scheduleListPreview = modaxBody.querySelector('.schedule-list-preview');
@@ -152,6 +188,7 @@
       event.preventDefault();
       const scheduleList = modaxBody.querySelector('#schedule-list');
       const confirmationContent = confirmationDialog.querySelector('.p-6');
+      confirmationContent.innerHTML = "Please confirm you want to send on the following schedule:"
       if (scheduleList) confirmationContent.appendChild(scheduleList);
       confirmationDialog.open = true;
     }
@@ -186,9 +223,11 @@
               hasError = true;
             }
           });
-          event.target.disabled = false;
-          if (hasError) confirmationDialog.open = false;
-          else window.location.href = '{% url "triggers.trigger_list" %}';
+          if (hasError) {
+            confirmationDialog.open = false;
+          } else {
+            window.location.href = '{% url "triggers.trigger_list" %}';
+          }
         });
     }
 
@@ -224,7 +263,7 @@
       initCalFields(form);
       onValueChange();
       const currentSubmit = dialogFooter.querySelector('temba-button[primary]');
-      const submitButton = createButton({ name: 'Create', onclick: showConfirmation, primary: true });
+      const submitButton = createButton({ name: 'Create', onclick: showConfirmation, primary: true, disabled: true });
       try {
         if (currentSubmit) {
           dialogFooter.removeChild(currentSubmit);