@@ -33,6 +33,10 @@ import {
   generalViewParam,
   generalViewUrlKeys,
 } from '@/app/workspace/[workspaceId]/settings/components/general/search-params'
+import {
+  getTimezonePickerPresentation,
+  timezonePreferenceFromPickerValue,
+} from '@/app/workspace/[workspaceId]/settings/components/general/timezone-picker'
 import type { SettingsAction } from '@/app/workspace/[workspaceId]/settings/components/settings-header/settings-header'
 import { SettingsPanel } from '@/app/workspace/[workspaceId]/settings/components/settings-panel'
 import { SettingsSection } from '@/app/workspace/[workspaceId]/settings/components/settings-section/settings-section'
@@ -221,7 +225,12 @@ export function General() {
   }
 
   const handleTimezoneChange = async (value: string) => {
-    await updateSetting.mutateAsync({ key: 'timezone', value })
+    const timezone = timezonePreferenceFromPickerValue(value)
+    if (timezone === undefined) return
+    await updateSetting.mutateAsync({
+      key: 'timezone',
+      value: timezone,
+    })
   }
 
   const handleAutoConnectChange = async (checked: boolean) => {
@@ -288,6 +297,14 @@ export function General() {
     return <SettingsPanel actions={actions} />
   }
 
+  const browserTimezone = getBrowserTimezone()
+  const savedTimezone = settings?.timezone ?? null
+  const timezonePicker = getTimezonePickerPresentation(
+    savedTimezone,
+    browserTimezone,
+    TIMEZONE_OPTIONS
+  )
+
   return (
     <>
       <SettingsPanel actions={actions}>
@@ -433,10 +450,10 @@ export function General() {
                   dropdownWidth={240}
                   searchable
                   searchPlaceholder='Search timezones'
-                  value={settings?.timezone ?? getBrowserTimezone()}
+                  value={timezonePicker.value}
                   onChange={handleTimezoneChange}
                   placeholder='Select timezone'
-                  options={TIMEZONE_OPTIONS}
+                  options={timezonePicker.options}
                 />
               </div>
             </div>
 
@@ -0,0 +1,63 @@
+/**
+ * @vitest-environment node
+ */
+import { describe, expect, it } from 'vitest'
+import {
+  AUTO_TIMEZONE_OPTION_VALUE,
+  getTimezonePickerPresentation,
+  INVALID_TIMEZONE_OPTION_VALUE,
+  timezonePreferenceFromPickerValue,
+} from '@/app/workspace/[workspaceId]/settings/components/general/timezone-picker'
+
+const timezoneOptions = [{ label: 'Los Angeles (GMT-07:00)', value: 'America/Los_Angeles' }]
+
+describe('getTimezonePickerPresentation', () => {
+  it('shows an unset preference as an explicit browser-managed option', () => {
+    expect(getTimezonePickerPresentation(null, 'America/Los_Angeles', timezoneOptions)).toEqual({
+      value: AUTO_TIMEZONE_OPTION_VALUE,
+      options: [
+        { label: 'Auto: Los Angeles (GMT-07:00)', value: AUTO_TIMEZONE_OPTION_VALUE },
+        ...timezoneOptions,
+      ],
+    })
+  })
+
+  it('keeps a valid saved timezone selected independently of Auto', () => {
+    expect(
+      getTimezonePickerPresentation('America/Los_Angeles', 'America/Los_Angeles', timezoneOptions)
+        .value
+    ).toBe('America/Los_Angeles')
+  })
+
+  it('adds a valid saved timezone that is absent from the curated options', () => {
+    expect(getTimezonePickerPresentation('Etc/GMT+5', 'UTC', timezoneOptions)).toEqual({
+      value: 'Etc/GMT+5',
+      options: [
+        { label: 'Auto: UTC', value: AUTO_TIMEZONE_OPTION_VALUE },
+        { label: 'Etc/GMT+5', value: 'Etc/GMT+5' },
+        ...timezoneOptions,
+      ],
+    })
+  })
+
+  it('surfaces an invalid saved timezone without making it selectable', () => {
+    expect(getTimezonePickerPresentation('Mars/Olympus', 'UTC', timezoneOptions)).toEqual({
+      value: INVALID_TIMEZONE_OPTION_VALUE,
+      options: [
+        { label: 'Auto: UTC', value: AUTO_TIMEZONE_OPTION_VALUE },
+        {
+          label: 'Invalid: Mars/Olympus',
+          value: INVALID_TIMEZONE_OPTION_VALUE,
+          disabled: true,
+        },
+        ...timezoneOptions,
+      ],
+    })
+  })
+
+  it('persists Auto as an unset preference', () => {
+    expect(timezonePreferenceFromPickerValue(AUTO_TIMEZONE_OPTION_VALUE)).toBeNull()
+    expect(timezonePreferenceFromPickerValue('Asia/Tokyo')).toBe('Asia/Tokyo')
+    expect(timezonePreferenceFromPickerValue(INVALID_TIMEZONE_OPTION_VALUE)).toBeUndefined()
+  })
+})
@@ -0,0 +1,62 @@
+import type { ComboboxOption } from '@sim/emcn'
+import { isValidTimezone, sanitizeTimezoneForDisplay } from '@/lib/core/utils/timezone'
+
+export const AUTO_TIMEZONE_OPTION_VALUE = '__auto_timezone__'
+export const INVALID_TIMEZONE_OPTION_VALUE = '__invalid_timezone__'
+
+interface TimezonePickerPresentation {
+  value: string
+  options: ComboboxOption[]
+}
+
+/** Builds the picker state without making an unset browser fallback look persisted. */
+export function getTimezonePickerPresentation(
+  savedTimezone: string | null,
+  browserTimezone: string,
+  timezoneOptions: readonly ComboboxOption[]
+): TimezonePickerPresentation {
+  const hasInvalidTimezone = savedTimezone !== null && !isValidTimezone(savedTimezone)
+  const unlistedTimezone =
+    savedTimezone !== null &&
+    !hasInvalidTimezone &&
+    !timezoneOptions.some((option) => option.value === savedTimezone)
+      ? savedTimezone
+      : null
+  const safeInvalidTimezone =
+    savedTimezone === null ? '' : sanitizeTimezoneForDisplay(savedTimezone)
+  const browserTimezoneLabel =
+    timezoneOptions.find((option) => option.value === browserTimezone)?.label ??
+    sanitizeTimezoneForDisplay(browserTimezone)
+
+  return {
+    value: hasInvalidTimezone
+      ? INVALID_TIMEZONE_OPTION_VALUE
+      : (savedTimezone ?? AUTO_TIMEZONE_OPTION_VALUE),
+    options: [
+      { label: `Auto: ${browserTimezoneLabel}`, value: AUTO_TIMEZONE_OPTION_VALUE },
+      ...(hasInvalidTimezone
+        ? [
+            {
+              label: `Invalid: ${safeInvalidTimezone || '(empty)'}`,
+              value: INVALID_TIMEZONE_OPTION_VALUE,
+              disabled: true,
+            },
+          ]
+        : []),
+      ...(unlistedTimezone
+        ? [
+            {
+              label: sanitizeTimezoneForDisplay(unlistedTimezone),
+              value: unlistedTimezone,
+            },
+          ]
+        : []),
+      ...timezoneOptions,
+    ],
+  }
+}
+
+export function timezonePreferenceFromPickerValue(value: string): string | null | undefined {
+  if (value === INVALID_TIMEZONE_OPTION_VALUE) return undefined
+  return value === AUTO_TIMEZONE_OPTION_VALUE ? null : value
+}
@@ -7,12 +7,14 @@ import { beforeEach, describe, expect, it, vi } from 'vitest'
 import type { TableInfo, TableRow } from '@/lib/table'
 import { RowModal } from '@/app/workspace/[workspaceId]/tables/[tableId]/components/row-modal/row-modal'
 
-const { mockUseTimezoneState, mockUpdateRow, mockDeleteRow, mockDeleteRows } = vi.hoisted(() => ({
-  mockUseTimezoneState: vi.fn(),
-  mockUpdateRow: vi.fn(),
-  mockDeleteRow: vi.fn(),
-  mockDeleteRows: vi.fn(),
-}))
+const { mockToastError, mockUseTimezoneState, mockUpdateRow, mockDeleteRow, mockDeleteRows } =
+  vi.hoisted(() => ({
+    mockToastError: vi.fn(),
+    mockUseTimezoneState: vi.fn(),
+    mockUpdateRow: vi.fn(),
+    mockDeleteRow: vi.fn(),
+    mockDeleteRows: vi.fn(),
+  }))
 
 vi.mock('next/navigation', () => ({
   useParams: () => ({ workspaceId: 'workspace-1' }),
@@ -29,6 +31,8 @@ vi.mock('@sim/emcn', () => {
   const passthrough = ({ children }: { children?: ReactNode }) => children ?? null
   return {
     Checkbox: () => null,
+    Chip: ({ children, ...props }: { children?: ReactNode }) =>
+      createElement('button', { type: 'button', ...props }, children),
     ChipConfirmModal: passthrough,
     ChipDatePicker: ({ value, onChange }: { value?: string; onChange: (value: string) => void }) =>
       createElement(
@@ -39,7 +43,27 @@ vi.mock('@sim/emcn', () => {
     ChipModal: passthrough,
     ChipModalBody: passthrough,
     ChipModalError: passthrough,
-    ChipModalField: passthrough,
+    ChipModalField: ({
+      type,
+      value,
+      onChange,
+      children,
+    }: {
+      type?: string
+      value?: string
+      onChange?: (value: string) => void
+      children?: ReactNode | ((aria: Record<string, string>) => ReactNode)
+    }) =>
+      type === 'input'
+        ? createElement('input', {
+            'data-testid': 'modal-input',
+            value: value ?? '',
+            onChange: (event: { currentTarget: { value: string } }) =>
+              onChange?.(event.currentTarget.value),
+          })
+        : typeof children === 'function'
+          ? children({ 'aria-describedby': 'field-hint' })
+          : (children ?? null),
     ChipModalFooter: ({
       primaryAction,
     }: {
@@ -64,6 +88,7 @@ vi.mock('@sim/emcn', () => {
           onChange(event.currentTarget.value),
       }),
     Label: passthrough,
+    toast: { error: mockToastError },
   }
 })
 
@@ -111,7 +136,9 @@ describe('RowModal expiration editing', () => {
     ;(globalThis as { IS_REACT_ACT_ENVIRONMENT?: boolean }).IS_REACT_ACT_ENVIRONMENT = true
     act(() => root.render(createElement(RowModal, props)))
 
-    expect(container.querySelector('[role="status"]')?.textContent).toBe('Loading timezone…')
+    expect(container.querySelector('[aria-label="Edit expires_at"]')?.textContent).toBe(
+      'Loading timezone…'
+    )
     expect(container.querySelector<HTMLInputElement>('[data-testid="time"]')).toBeNull()
     expect(container.querySelector<HTMLButtonElement>('[data-testid="submit"]')?.disabled).toBe(
       true
@@ -145,4 +172,129 @@ describe('RowModal expiration editing', () => {
     act(() => root.unmount())
     container.remove()
   })
+
+  it('also waits for timezone settings on an ordinary Date column', () => {
+    mockUseTimezoneState.mockReturnValue({ timezone: 'Asia/Tokyo', status: 'loading' })
+    const container = document.createElement('div')
+    document.body.appendChild(container)
+    const root = createRoot(container)
+    const props = {
+      mode: 'edit' as const,
+      isOpen: true,
+      onClose: vi.fn(),
+      table: {
+        id: 'table-2',
+        name: 'Dates',
+        schema: { columns: [{ name: 'starts_at', type: 'date' as const }] },
+      },
+      row: { ...row, data: { starts_at: '2026-06-15T09:00:00+09:00' } },
+      onSuccess: vi.fn(),
+    }
+
+    act(() => root.render(createElement(RowModal, props)))
+
+    expect(container.querySelector('[aria-label="Edit starts_at"]')?.textContent).toBe(
+      'Loading timezone…'
+    )
+    expect(container.querySelector<HTMLInputElement>('[data-testid="time"]')).toBeNull()
+
+    mockUseTimezoneState.mockReturnValue({
+      timezone: 'America/Los_Angeles',
+      status: 'ready',
+    })
+    act(() => root.render(createElement(RowModal, props)))
+
+    expect(container.querySelector<HTMLInputElement>('[data-testid="time"]')).not.toBeNull()
+    act(() => root.unmount())
+    container.remove()
+  })
+
+  it('blocks an invalid saved timezone with the plain-text guidance', () => {
+    mockUseTimezoneState.mockReturnValue({
+      timezone: 'America/Los_Angeles',
+      savedTimezone: 'Mars/Olympus',
+      status: 'invalid',
+    })
+    const container = document.createElement('div')
+    document.body.appendChild(container)
+    const root = createRoot(container)
+    const props = {
+      mode: 'edit' as const,
+      isOpen: true,
+      onClose: vi.fn(),
+      table,
+      row,
+      onSuccess: vi.fn(),
+    }
+
+    act(() => root.render(createElement(RowModal, props)))
+
+    const blockedField = container.querySelector<HTMLButtonElement>(
+      '[aria-label="Edit expires_at"]'
+    )
+    expect(blockedField?.textContent).toBe(String(row.data.expires_at))
+    expect(container.querySelector<HTMLButtonElement>('[data-testid="submit"]')?.disabled).toBe(
+      true
+    )
+    expect(mockToastError).not.toHaveBeenCalled()
+    act(() => blockedField?.click())
+    expect(mockToastError).toHaveBeenCalledWith(
+      'Your saved timezone “Mars/Olympus” is invalid. Update it in Settings → General before editing Date or Expiration cells.'
+    )
+    act(() => root.unmount())
+    container.remove()
+  })
+
+  it('keeps unrelated fields editable and omits blocked date values from the update', async () => {
+    mockUseTimezoneState.mockReturnValue({
+      timezone: 'America/Los_Angeles',
+      savedTimezone: 'Mars/Olympus',
+      status: 'invalid',
+    })
+    const container = document.createElement('div')
+    document.body.appendChild(container)
+    const root = createRoot(container)
+    const mixedTable: TableInfo = {
+      ...table,
+      schema: {
+        columns: [
+          { name: 'name', type: 'string' },
+          { name: 'expires_at', type: 'ttl' },
+        ],
+      },
+    }
+    const mixedRow = { ...row, data: { name: 'Ada', expires_at: row.data.expires_at } }
+    const props = {
+      mode: 'edit' as const,
+      isOpen: true,
+      onClose: vi.fn(),
+      table: mixedTable,
+      row: mixedRow,
+      onSuccess: vi.fn(),
+    }
+
+    act(() => root.render(createElement(RowModal, props)))
+
+    const nameInput = container.querySelector<HTMLInputElement>('[data-testid="modal-input"]')
+    const blockedField = container.querySelector<HTMLButtonElement>(
+      '[aria-label="Edit expires_at"]'
+    )
+    const submit = container.querySelector<HTMLButtonElement>('[data-testid="submit"]')
+    expect(nameInput?.value).toBe('Ada')
+    expect(blockedField?.textContent).toBe(String(row.data.expires_at))
+    expect(submit?.disabled).toBe(false)
+
+    act(() => changeInput(nameInput as HTMLInputElement, 'Grace'))
+    await act(async () => submit?.click())
+
+    expect(mockUpdateRow).toHaveBeenCalledWith({
+      rowId: 'row-1',
+      data: { name: 'Grace' },
+    })
+    expect(props.onSuccess).toHaveBeenCalledTimes(1)
+    expect(mockToastError).not.toHaveBeenCalled()
+
+    act(() => root.unmount())
+    container.remove()
+  })
 })