feat(ui): replace end date field with '...' button toggle

- Hide end date by default; reveal via '...' button in both modes
- Keep state/validation/API logic unchanged
- Normalize labels to use MUI TextField labels across modes
- Align button with fields; constrain widths for expanded mode

src/components/Event/EventFormFields.tsx

@@ -38,6 +38,7 @@ import { FieldWithLabel } from "./components/FieldWithLabel";
 import { DateTimeFields } from "./components/DateTimeFields";
 import { useAllDayToggle } from "./hooks/useAllDayToggle";
 import { splitDateTime, combineDateTime } from "./utils/dateTimeHelpers";
+import { getEndDateForStartChange } from "./utils/dateRules";
 import {
   formatLocalDateTime,
   formatDateTimeInTimezone,
@@ -163,6 +164,9 @@ export default function EventFormFields({
   const [endDate, setEndDate] = React.useState("");
   const [endTime, setEndTime] = React.useState("");
 
+  // UI state for showing/hiding end date field
+  const [showEndDate, setShowEndDate] = React.useState(false);
+
   // Use all-day toggle hook
   const { originalTimeRef, handleAllDayToggle } = useAllDayToggle({
     allday,
@@ -268,13 +272,25 @@ export default function EventFormFields({
     (newDate: string) => {
       setStartDate(newDate);
       const newStart = combineDateTime(newDate, startTime);
+
+      // Update start
       if (onStartChange) {
         onStartChange(newStart);
       } else {
         setStart(newStart);
       }
+
+      // Rule: update end date when start date changes
+      const nextEndDate = getEndDateForStartChange(newDate, allday);
+      setEndDate(nextEndDate);
+      const newEnd = combineDateTime(nextEndDate, endTime || startTime);
+      if (onEndChange) {
+        onEndChange(newEnd);
+      } else {
+        setEnd(newEnd);
+      }
     },
-    [startTime, onStartChange, setStart]
+    [startTime, endTime, onStartChange, onEndChange, setStart, setEnd, allday]
   );
 
   const handleStartTimeChange = React.useCallback(
@@ -343,6 +359,35 @@ export default function EventFormFields({
     onValidationChange?.(validation.isValid);
   }, [validateForm, onValidationChange]);
 
+  // Auto-calculate end date from start date if not already set
+  React.useEffect(() => {
+    if (startDate && !endDate) {
+      setEndDate(startDate);
+      const newEnd = combineDateTime(startDate, endTime || startTime);
+      if (onEndChange) {
+        onEndChange(newEnd);
+      } else {
+        setEnd(newEnd);
+      }
+    }
+  }, [startDate, endDate, startTime, endTime, onEndChange, setEnd]);
+
+  // Auto-calculate end time from start time (+ 1 hour) if not already set
+  React.useEffect(() => {
+    if (startTime && !endTime && !allday) {
+      const [hours, minutes] = startTime.split(":");
+      const endHour = (parseInt(hours) + 1) % 24;
+      const calculatedEndTime = `${endHour.toString().padStart(2, "0")}:${minutes}`;
+      setEndTime(calculatedEndTime);
+      const newEnd = combineDateTime(endDate || startDate, calculatedEndTime);
+      if (onEndChange) {
+        onEndChange(newEnd);
+      } else {
+        setEnd(newEnd);
+      }
+    }
+  }, [startTime, endTime, allday, endDate, startDate, onEndChange, setEnd]);
+
   const validation = validateForm();
 
   const handleAddVideoConference = () => {
@@ -465,6 +510,8 @@ export default function EventFormFields({
           onStartTimeChange={handleStartTimeChange}
           onEndDateChange={handleEndDateChange}
           onEndTimeChange={handleEndTimeChange}
+          showEndDate={showEndDate}
+          onToggleEndDate={() => setShowEndDate(!showEndDate)}
         />
       </FieldWithLabel>
 

src/components/Event/components/DateTimeFields.tsx

@@ -1,9 +1,10 @@
 import React from "react";
-import { Box, Typography } from "@mui/material";
+import { Box, IconButton, Tooltip, Typography } from "@mui/material";
 import { DatePicker } from "@mui/x-date-pickers/DatePicker";
 import { TimePicker } from "@mui/x-date-pickers/TimePicker";
 import { LocalizationProvider } from "@mui/x-date-pickers/LocalizationProvider";
 import { AdapterMoment } from "@mui/x-date-pickers/AdapterMoment";
+import MoreHorizIcon from "@mui/icons-material/MoreHoriz";
 import moment, { Moment } from "moment";
 
 /**
@@ -16,6 +17,8 @@ export interface DateTimeFieldsProps {
   endTime: string;
   allday: boolean;
   showMore: boolean;
+  showEndDate: boolean;
+  onToggleEndDate: () => void;
   validation: {
     errors: {
       dateTime: string;
@@ -38,6 +41,8 @@ export const DateTimeFields: React.FC<DateTimeFieldsProps> = ({
   endTime,
   allday,
   showMore,
+  showEndDate,
+  onToggleEndDate,
   validation,
   onStartDateChange,
   onStartTimeChange,
@@ -46,18 +51,18 @@ export const DateTimeFields: React.FC<DateTimeFieldsProps> = ({
 }) => {
   return (
     <LocalizationProvider dateAdapter={AdapterMoment} adapterLocale="en">
-      <Box display="flex" gap={1} flexDirection="column">
+      <Box
+        display="flex"
+        gap={1}
+        flexDirection="column"
+        sx={{ maxWidth: showMore ? "calc(100% - 145px)" : "100%" }}
+      >
         {/* First row: 4 fields */}
-        <Box display="flex" gap={1} flexDirection="row" alignItems="flex-start">
+        <Box display="flex" gap={1} flexDirection="row" alignItems="center">
           {/* Start Date - 30% */}
-          <Box sx={{ flexGrow: 0.3, flexBasis: "25%", minWidth: 0 }}>
-            {showMore && (
-              <Typography variant="caption" display="block" mb={0.5}>
-                Start Date
-              </Typography>
-            )}
+          <Box sx={{ flexGrow: 0.3, flexBasis: "25%", maxWidth: "150px" }}>
             <DatePicker
-              label={!showMore ? "Start Date" : ""}
+              label="Start Date"
               value={startDate ? moment(startDate) : null}
               onChange={(newValue: Moment | null) => {
                 onStartDateChange(newValue?.format("YYYY-MM-DD") || "");
@@ -68,22 +73,17 @@ export const DateTimeFields: React.FC<DateTimeFieldsProps> = ({
                   margin: "dense" as const,
                   fullWidth: true,
                   InputLabelProps: { shrink: true },
-                  "data-testid": "start-date-input",
                   sx: { width: "100%" },
+                  inputProps: { "data-testid": "start-date-input" },
                 },
               }}
             />
           </Box>
 
           {/* Start Time - 20% */}
-          <Box sx={{ flexGrow: 0.2, flexBasis: "25%", minWidth: 0 }}>
-            {showMore && (
-              <Typography variant="caption" display="block" mb={0.5}>
-                Start Time
-              </Typography>
-            )}
+          <Box sx={{ flexGrow: 0.2, flexBasis: "25%", maxWidth: "150px" }}>
             <TimePicker
-              label={!showMore ? "Start Time" : ""}
+              label="Start Time"
               value={startTime ? moment(startTime, "HH:mm") : null}
               onChange={(newValue: Moment | null) => {
                 onStartTimeChange(newValue?.format("HH:mm") || "");
@@ -95,22 +95,17 @@ export const DateTimeFields: React.FC<DateTimeFieldsProps> = ({
                   margin: "dense" as const,
                   fullWidth: true,
                   InputLabelProps: { shrink: true },
-                  "data-testid": "start-time-input",
                   sx: { width: "100%" },
+                  inputProps: { "data-testid": "start-time-input" },
                 },
               }}
             />
           </Box>
 
           {/* End Time - 20% */}
-          <Box sx={{ flexGrow: 0.2, flexBasis: "25%", minWidth: 0 }}>
-            {showMore && (
-              <Typography variant="caption" display="block" mb={0.5}>
-                End Time
-              </Typography>
-            )}
+          <Box sx={{ flexGrow: 0.2, flexBasis: "25%", maxWidth: "150px" }}>
             <TimePicker
-              label={!showMore ? "End Time" : ""}
+              label="End Time"
               value={endTime ? moment(endTime, "HH:mm") : null}
               onChange={(newValue: Moment | null) => {
                 onEndTimeChange(newValue?.format("HH:mm") || "");
@@ -123,38 +118,53 @@ export const DateTimeFields: React.FC<DateTimeFieldsProps> = ({
                   fullWidth: true,
                   InputLabelProps: { shrink: true },
                   error: !!validation.errors.dateTime,
-                  "data-testid": "end-time-input",
                   sx: { width: "100%" },
+                  inputProps: { "data-testid": "end-time-input" },
                 },
               }}
             />
           </Box>
 
-          {/* End Date - 30% */}
-          <Box sx={{ flexGrow: 0.3, flexBasis: "25%", minWidth: 0 }}>
-            {showMore && (
-              <Typography variant="caption" display="block" mb={0.5}>
-                End Date
-              </Typography>
+          {/* End Date - Conditional rendering */}
+          <Box sx={{ flexGrow: 0.3, flexBasis: "25%", maxWidth: "150px" }}>
+            {!showEndDate ? (
+              // Show "..." button to reveal end date
+              <Box
+                display="flex"
+                justifyContent="flex-start"
+                sx={{ mt: showMore ? 0 : 0 }}
+              >
+                <Tooltip title="Show end date">
+                  <IconButton
+                    size="small"
+                    onClick={onToggleEndDate}
+                    aria-label="Show end date"
+                  >
+                    <MoreHorizIcon />
+                  </IconButton>
+                </Tooltip>
+              </Box>
+            ) : (
+              // Show End Date picker (no hide button)
+              <DatePicker
+                label="End Date"
+                value={endDate ? moment(endDate) : null}
+                onChange={(newValue: Moment | null) => {
+                  onEndDateChange(newValue?.format("YYYY-MM-DD") || "");
+                }}
+                slotProps={{
+                  textField: {
+                    size: "small",
+                    margin: "dense" as const,
+                    fullWidth: true,
+                    InputLabelProps: { shrink: true },
+                    error: !!validation.errors.dateTime,
+                    sx: { width: "100%" },
+                    inputProps: { "data-testid": "end-date-input" },
+                  },
+                }}
+              />
             )}
-            <DatePicker
-              label={!showMore ? "End Date" : ""}
-              value={endDate ? moment(endDate) : null}
-              onChange={(newValue: Moment | null) => {
-                onEndDateChange(newValue?.format("YYYY-MM-DD") || "");
-              }}
-              slotProps={{
-                textField: {
-                  size: "small",
-                  margin: "dense" as const,
-                  fullWidth: true,
-                  InputLabelProps: { shrink: true },
-                  error: !!validation.errors.dateTime,
-                  "data-testid": "end-date-input",
-                  sx: { width: "100%" },
-                },
-              }}
-            />
           </Box>
         </Box>
 

src/components/Event/hooks/useAllDayToggle.ts

@@ -1,5 +1,6 @@
 import React from "react";
 import { combineDateTime } from "../utils/dateTimeHelpers";
+import { getEndDateForToggle } from "../utils/dateRules";
 import { getRoundedCurrentTime } from "../utils/dateTimeFormatters";
 
 /**
@@ -86,15 +87,15 @@ export function useAllDayToggle(
       setStartTime("");
       setEndTime("");
       newStart = startDate;
-      newEnd = endDate;
-
-      // If same day, extend end to next day
-      if (startDate === endDate) {
-        const nextDay = new Date(endDate);
-        nextDay.setDate(nextDay.getDate() + 1);
-        newEnd = nextDay.toISOString().split("T")[0];
-        setEndDate(newEnd); // Update internal endDate state
-      }
+      const nextEndDate = getEndDateForToggle({
+        nextAllDay: true,
+        fromAllDaySlot: !!originalTimeRef.current?.fromAllDaySlot,
+        startDate,
+        previousEndDate: endDate,
+        originalEndDate: originalTimeRef.current?.endDate,
+      });
+      newEnd = nextEndDate;
+      setEndDate(nextEndDate);
     } else {
       // ON => OFF: Restore original time AND original end date
       if (originalTimeRef.current) {
@@ -123,7 +124,12 @@ export function useAllDayToggle(
           setEndDate(startDate); // Set endDate = startDate
         } else {
           // Normal case: restore original time AND original end date
-          const restoredEndDate = originalTimeRef.current.endDate || endDate;
+          const restoredEndDate = getEndDateForToggle({
+            nextAllDay: false,
+            startDate,
+            previousEndDate: endDate,
+            originalEndDate: originalTimeRef.current.endDate,
+          });
 
           newStart = combineDateTime(startDate, originalTimeRef.current.start);
           newEnd = combineDateTime(

src/components/Event/utils/dateRules.ts

@@ -0,0 +1,62 @@
+// Date rules helpers to normalize end date/time behavior
+
+import { combineDateTime } from "./dateTimeHelpers";
+
+/** Adds a number of days to a YYYY-MM-DD string and returns YYYY-MM-DD */
+export function addDays(dateStr: string, days: number): string {
+  const d = new Date(dateStr);
+  d.setDate(d.getDate() + days);
+  return d.toISOString().split("T")[0];
+}
+
+/**
+ * Compute endDate (YYYY-MM-DD) when startDate changes
+ * - If all-day: endDate = startDate + 1 day
+ * - Else: endDate = startDate
+ */
+export function getEndDateForStartChange(
+  startDate: string,
+  isAllDay: boolean
+): string {
+  if (!startDate) return "";
+  return isAllDay ? addDays(startDate, 1) : startDate;
+}
+
+/**
+ * Compute new start/end (ISO-like strings) when toggling all-day
+ * - nextAllDay = true:
+ *   - If fromAllDaySlot: endDate = startDate
+ *   - Else: endDate = startDate + 1 day
+ *   - Times are cleared (date-only)
+ * - nextAllDay = false:
+ *   - end restored from originalEndDate if any, else previousEndDate, else start
+ */
+export function getEndDateForToggle(params: {
+  nextAllDay: boolean;
+  fromAllDaySlot?: boolean;
+  startDate: string;
+  previousEndDate: string;
+  originalEndDate?: string;
+}): string {
+  const {
+    nextAllDay,
+    fromAllDaySlot,
+    startDate,
+    previousEndDate,
+    originalEndDate,
+  } = params;
+  if (nextAllDay) {
+    return fromAllDaySlot ? startDate : addDays(startDate, 1);
+  }
+  return originalEndDate || previousEndDate || startDate;
+}
+
+/** Utility to combine date with a fallback time (HH:mm) safely */
+export function combineWithFallback(
+  dateStr: string,
+  timeHHmm: string | undefined,
+  fallbackTime: string
+): string {
+  const time = timeHHmm && timeHHmm.trim() ? timeHHmm : fallbackTime;
+  return combineDateTime(dateStr, time);
+}