diff --git a/README.md b/README.md
index 0f9b94a0..00cfc613 100644
--- a/README.md
+++ b/README.md
@@ -54,3 +54,10 @@ The new version is not deployed yet.
 - Shared locality validation enforces combined pollen constraint `AP + NAP + OP <= 100` and surfaces the same message in form validation feedback.
 - Backend locality write validation now evaluates pollen totals with full update context so partial updates cannot bypass the combined-value rule.
 - API tests include invalid create/update pollen payload coverage for non-integer, out-of-range, and total-above-100 cases.
+
+### Reviewer notes: Locality age method persistence
+
+- In Locality edit mode, the Age tab now preserves method-specific values when switching Dating method between `Time unit`, `Absolute`, and `Composite`.
+- Switching methods restores previously entered age values (e.g., `min_age`, `max_age`, basis/fraction selections) instead of clearing them.
+- Locality age validation now evaluates required basis fields against the currently active dating method, while allowing preserved values from other methods to remain in draft state.
+- See [documentation/CHANGELOG.md](documentation/CHANGELOG.md) for release-level tracking.
diff --git a/documentation/CHANGELOG.md b/documentation/CHANGELOG.md
index eead4a6c..25910e96 100644
--- a/documentation/CHANGELOG.md
+++ b/documentation/CHANGELOG.md
@@ -8,6 +8,8 @@
 ### Fixed
 - Resolved Update log detail navigation so Return buttons honor the originating table using the new shared return-navigation helper.
 - Restored Locality edit view synonym creation so saving a valid synonym immediately appears in the Synonyms table.
+- Locality Age tab now preserves age-entry drafts per dating method (`time_unit`, `absolute`, `composite`) so switching methods no longer clears previously entered min/max age and basis values.
+- Locality age validation now enforces required age-basis rules against the active dating method while tolerating preserved values from non-active methods.
 
 ### Added
 - Species table Genus and Species filters now also match synonym names (syn_genus_name and syn_species_name) returned with each species record.
diff --git a/frontend/src/components/DetailView/Context/DetailContext.tsx b/frontend/src/components/DetailView/Context/DetailContext.tsx
index d085a0a4..a8b18cc1 100755
--- a/frontend/src/components/DetailView/Context/DetailContext.tsx
+++ b/frontend/src/components/DetailView/Context/DetailContext.tsx
@@ -58,7 +58,7 @@ export type DetailContextType<T> = {
   mode: ModeType
   setMode: (newMode: ModeOptions) => void
   editData: EditDataType<T>
-  setEditData: (editData: EditDataType<T>) => void
+  setEditData: SetEditDataType<T>
   textField: (field: keyof EditDataType<T>, options?: TextFieldOptions) => JSX.Element
   bigTextField: (field: keyof EditDataType<T>) => JSX.Element
   dropdown: (
@@ -87,6 +87,8 @@ export type DetailContextType<T> = {
   resetEditData: () => void
 }
 
+export type SetEditDataType<T> = (editData: EditDataType<T>) => void
+
 export const DetailContext = createContext<DetailContextType<unknown>>(null!)
 
 export const makeEditData = <T,>(data: T): EditDataType<T> => ({
diff --git a/frontend/src/components/DetailView/common/editingComponents.test.tsx b/frontend/src/components/DetailView/common/editingComponents.test.tsx
index a3f78ab7..9285f6f0 100644
--- a/frontend/src/components/DetailView/common/editingComponents.test.tsx
+++ b/frontend/src/components/DetailView/common/editingComponents.test.tsx
@@ -61,6 +61,45 @@ const Wrapper = ({ children }: { children: ReactNode }) => {
   )
 }
 
+const FractionUpdateWrapper = () => {
+  const initialEditData = {
+    min_age: 10,
+    max_age: 20,
+    frac_min: '',
+    bfa_min: '',
+  } as unknown as EditDataType<LocalityDetailsType>
+
+  const [editData, setEditData] = useState<EditDataType<LocalityDetailsType>>(initialEditData)
+
+  const contextValue: DetailContextType<LocalityDetailsType> = {
+    data: initialEditData as unknown as LocalityDetailsType,
+    mode: modeOptionToMode.edit,
+    setMode: () => undefined,
+    editData,
+    setEditData,
+    isDirty: false,
+    resetEditData: () => setEditData(initialEditData),
+    textField: () => <></>,
+    bigTextField: () => <></>,
+    dropdown: () => <></>,
+    dropdownWithSearch: () => <></>,
+    radioSelection: () => <></>,
+    validator: () => ({ name: '', error: null }),
+    fieldsWithErrors: {},
+    setFieldsWithErrors: () => undefined,
+  }
+
+  return (
+    <DetailContext.Provider value={contextValue as DetailContextType<unknown>}>
+      <div data-testid="min-age">{editData.min_age}</div>
+      <button type="button" onClick={() => setEditData({ ...editData, frac_min: '1:2' })}>
+        set fraction 1:2
+      </button>
+      <BasisForAgeSelection targetField="bfa_min" fraction={editData.frac_min} selectorTable={<SelectorTable />} />
+    </DetailContext.Provider>
+  )
+}
+
 describe('BasisForAgeSelection', () => {
   it('keeps minimum age populated when selecting a time unit without a fraction', async () => {
     const user = userEvent.setup()
@@ -83,4 +122,23 @@ describe('BasisForAgeSelection', () => {
       expect(updatedBasisField.value).toBe('abdounian')
     })
   })
+
+  it('recalculates minimum age when fraction changes after selecting a time unit', async () => {
+    const user = userEvent.setup()
+
+    render(<FractionUpdateWrapper />)
+
+    await user.click(screen.getByRole('textbox'))
+    await user.click(screen.getByRole('button', { name: /choose time unit/i }))
+
+    await waitFor(() => {
+      expect(screen.getByTestId('min-age').textContent).toContain('45')
+    })
+
+    await user.click(screen.getByRole('button', { name: /set fraction 1:2/i }))
+
+    await waitFor(() => {
+      expect(screen.getByTestId('min-age').textContent).toContain('42.5')
+    })
+  })
 })
diff --git a/frontend/src/components/Locality/Tabs/AgeTab.test.tsx b/frontend/src/components/Locality/Tabs/AgeTab.test.tsx
new file mode 100644
index 00000000..149640fe
--- /dev/null
+++ b/frontend/src/components/Locality/Tabs/AgeTab.test.tsx
@@ -0,0 +1,196 @@
+import { describe, expect, it, jest } from '@jest/globals'
+import { render, screen } from '@testing-library/react'
+import userEvent from '@testing-library/user-event'
+import { ReactNode, useState } from 'react'
+import { AgeTab } from './AgeTab'
+import { DetailContext, DetailContextType, modeOptionToMode } from '@/components/DetailView/Context/DetailContext'
+import { EditDataType, LocalityDetailsType } from '@/shared/types'
+import { DropdownOption } from '@/components/DetailView/common/editingComponents'
+import { OptionalRadioSelectionProps, TextFieldOptions } from '@/components/DetailView/DetailView'
+import '@testing-library/jest-dom'
+
+jest.mock('@/redux/timeUnitReducer', () => ({
+  useGetTimeUnitDetailsQuery: () => ({ data: undefined, isFetching: false }),
+}))
+
+jest.mock('@/components/TimeUnit/TimeUnitTable', () => ({
+  TimeUnitTable: () => <div>TimeUnitTable</div>,
+}))
+
+const toDisplayValue = (option: DropdownOption | string): string => {
+  if (typeof option === 'string') return option
+  return option.display
+}
+
+const toRawValue = (option: DropdownOption | string): number | string | boolean => {
+  if (typeof option === 'string') return option
+  return option.value
+}
+
+const initialEditData = {
+  date_meth: 'time_unit',
+  min_age: 10,
+  max_age: 20,
+  bfa_min_abs: '',
+  bfa_max_abs: '',
+  bfa_min: 'tu-min-initial',
+  bfa_max: 'tu-max-initial',
+  frac_min: '1:2',
+  frac_max: '2:2',
+  chron: '',
+  age_comm: '',
+} as unknown as EditDataType<LocalityDetailsType>
+
+const toInputValue = (value: unknown): string => {
+  if (typeof value === 'string' || typeof value === 'number') return String(value)
+  return ''
+}
+
+const ContextWrapper = ({ children }: { children: ReactNode }) => {
+  const [editData, setEditData] = useState<EditDataType<LocalityDetailsType>>(initialEditData)
+
+  const setFieldValue = (field: keyof EditDataType<LocalityDetailsType>, value: string) => {
+    setEditData(prev => ({
+      ...prev,
+      [field]: value === '' ? '' : Number.isNaN(Number(value)) ? value : Number(value),
+    }))
+  }
+
+  const contextValue: DetailContextType<LocalityDetailsType> = {
+    data: initialEditData as unknown as LocalityDetailsType,
+    mode: modeOptionToMode.edit,
+    setMode: () => undefined,
+    editData,
+    setEditData,
+    isDirty: false,
+    resetEditData: () => setEditData(initialEditData),
+    textField: (field: keyof EditDataType<LocalityDetailsType>, options?: TextFieldOptions) => (
+      <input
+        aria-label={String(field)}
+        value={toInputValue(editData[field])}
+        readOnly={options?.readonly}
+        onChange={event => setFieldValue(field, event.currentTarget.value)}
+      />
+    ),
+    bigTextField: (field: keyof EditDataType<LocalityDetailsType>) => (
+      <textarea
+        aria-label={String(field)}
+        value={toInputValue(editData[field])}
+        onChange={event => setFieldValue(field, event.currentTarget.value)}
+      />
+    ),
+    dropdown: (field: keyof EditDataType<LocalityDetailsType>) => (
+      <input
+        aria-label={String(field)}
+        value={toInputValue(editData[field])}
+        onChange={event => setFieldValue(field, event.currentTarget.value)}
+      />
+    ),
+    dropdownWithSearch: () => <></>,
+    radioSelection: (
+      field: keyof EditDataType<LocalityDetailsType>,
+      options: Array<DropdownOption | string>,
+      _name: string,
+      optionalRadioSelectionProps?: OptionalRadioSelectionProps
+    ) => (
+      <>
+        {options.map(option => (
+          <button
+            key={String(toRawValue(option))}
+            type="button"
+            onClick={() => {
+              const value = toRawValue(option)
+              if (optionalRadioSelectionProps?.handleSetEditData) {
+                optionalRadioSelectionProps.handleSetEditData(value)
+                return
+              }
+              setEditData(prev => ({ ...prev, [field]: value }))
+            }}
+          >
+            {toDisplayValue(option)}
+          </button>
+        ))}
+      </>
+    ),
+    validator: () => ({ name: '', error: null }),
+    fieldsWithErrors: {},
+    setFieldsWithErrors: () => undefined,
+  }
+
+  return <DetailContext.Provider value={contextValue as DetailContextType<unknown>}>{children}</DetailContext.Provider>
+}
+
+describe('AgeTab', () => {
+  it('preserves per-method age drafts while switching dating method', async () => {
+    const user = userEvent.setup()
+
+    render(
+      <ContextWrapper>
+        <AgeTab />
+      </ContextWrapper>
+    )
+
+    await user.click(screen.getByRole('button', { name: 'Composite' }))
+
+    const minAgeInput = screen.getByLabelText('min_age')
+    const maxAgeInput = screen.getByLabelText('max_age')
+
+    await user.clear(minAgeInput)
+    await user.type(minAgeInput, '1.5')
+    await user.clear(maxAgeInput)
+    await user.type(maxAgeInput, '2.5')
+    const minAbsInput = screen.getByLabelText('bfa_min_abs')
+    const maxAbsInput = screen.getByLabelText('bfa_max_abs')
+
+    await user.clear(minAbsInput)
+    await user.type(minAbsInput, 'AAR')
+    await user.clear(maxAbsInput)
+    await user.type(maxAbsInput, 'C14')
+
+    await user.click(screen.getByRole('button', { name: 'Time unit' }))
+
+    expect(screen.getByLabelText<HTMLInputElement>('min_age').value).toBe('10')
+    expect(screen.getByLabelText<HTMLInputElement>('max_age').value).toBe('20')
+    expect(screen.getByLabelText<HTMLInputElement>('bfa_min').value).toBe('tu-min-initial')
+    expect(screen.getByLabelText<HTMLInputElement>('bfa_max').value).toBe('tu-max-initial')
+    expect(screen.getByLabelText<HTMLInputElement>('frac_min').value).toBe('1:2')
+    expect(screen.getByLabelText<HTMLInputElement>('frac_max').value).toBe('2:2')
+
+    await user.click(screen.getByRole('button', { name: 'Composite' }))
+
+    expect(screen.getByLabelText<HTMLInputElement>('min_age').value).toBe('1.5')
+    expect(screen.getByLabelText<HTMLInputElement>('max_age').value).toBe('2.5')
+    expect(screen.getByLabelText<HTMLInputElement>('bfa_min_abs').value).toBe('AAR')
+    expect(screen.getByLabelText<HTMLInputElement>('bfa_max_abs').value).toBe('C14')
+  })
+
+  it('restores time_unit values after a composite ↔ time_unit round-trip', async () => {
+    const user = userEvent.setup()
+
+    render(
+      <ContextWrapper>
+        <AgeTab />
+      </ContextWrapper>
+    )
+
+    await user.click(screen.getByRole('button', { name: 'Composite' }))
+
+    await user.clear(screen.getByLabelText('min_age'))
+    await user.type(screen.getByLabelText('min_age'), '3.1')
+    await user.clear(screen.getByLabelText('max_age'))
+    await user.type(screen.getByLabelText('max_age'), '3.9')
+
+    await user.click(screen.getByRole('button', { name: 'Time unit' }))
+    await user.click(screen.getByRole('button', { name: 'Composite' }))
+
+    expect(screen.getByLabelText<HTMLInputElement>('min_age').value).toBe('3.1')
+    expect(screen.getByLabelText<HTMLInputElement>('max_age').value).toBe('3.9')
+
+    await user.click(screen.getByRole('button', { name: 'Time unit' }))
+
+    expect(screen.getByLabelText<HTMLInputElement>('min_age').value).toBe('10')
+    expect(screen.getByLabelText<HTMLInputElement>('max_age').value).toBe('20')
+    expect(screen.getByLabelText<HTMLInputElement>('bfa_min').value).toBe('tu-min-initial')
+    expect(screen.getByLabelText<HTMLInputElement>('bfa_max').value).toBe('tu-max-initial')
+  })
+})
diff --git a/frontend/src/components/Locality/Tabs/AgeTab.tsx b/frontend/src/components/Locality/Tabs/AgeTab.tsx
index d81ff6de..abff3f54 100755
--- a/frontend/src/components/Locality/Tabs/AgeTab.tsx
+++ b/frontend/src/components/Locality/Tabs/AgeTab.tsx
@@ -1,20 +1,75 @@
-import { LocalityDetailsType } from '@/shared/types'
+import { EditDataType, LocalityDetailsType } from '@/shared/types'
 import { BasisForAgeSelection } from '@/components/DetailView/common/editingComponents'
 import { emptyOption } from '@/components/DetailView/common/misc'
 import { ArrayFrame, HalfFrames } from '@/components/DetailView/common/tabLayoutHelpers'
-import { useDetailContext } from '@/components/DetailView/Context/DetailContext'
+import { makeEditData, useDetailContext } from '@/components/DetailView/Context/DetailContext'
 import { TimeUnitTable } from '@/components/TimeUnit/TimeUnitTable'
 import { useGetTimeUnitDetailsQuery } from '@/redux/timeUnitReducer'
 import { skipToken } from '@reduxjs/toolkit/query'
 import { CircularProgress } from '@mui/material'
+import { useEffect, useState } from 'react'
+
+type LocalityDatingMethod = 'time_unit' | 'absolute' | 'composite'
+
+type AgeFields = Pick<
+  EditDataType<LocalityDetailsType>,
+  'min_age' | 'bfa_min_abs' | 'bfa_min' | 'frac_min' | 'max_age' | 'bfa_max_abs' | 'bfa_max' | 'frac_max'
+>
+
+type AgeDraftsByMethod = Record<LocalityDatingMethod, AgeFields>
+
+const emptyAgeFields = (): AgeFields => ({
+  min_age: undefined,
+  bfa_min_abs: '',
+  bfa_min: '',
+  frac_min: '',
+  max_age: undefined,
+  bfa_max_abs: '',
+  bfa_max: '',
+  frac_max: '',
+})
+
+const getAgeFields = (editData: EditDataType<LocalityDetailsType>): AgeFields => ({
+  min_age: editData.min_age,
+  bfa_min_abs: editData.bfa_min_abs,
+  bfa_min: editData.bfa_min,
+  frac_min: editData.frac_min,
+  max_age: editData.max_age,
+  bfa_max_abs: editData.bfa_max_abs,
+  bfa_max: editData.bfa_max,
+  frac_max: editData.frac_max,
+})
+
+const toDatingMethod = (value: number | string | boolean | undefined): LocalityDatingMethod | null => {
+  if (value === 'time_unit' || value === 'absolute' || value === 'composite') return value
+  return null
+}
+
+const initializeDrafts = (editData: EditDataType<LocalityDetailsType>): AgeDraftsByMethod => {
+  const drafts = {
+    time_unit: emptyAgeFields(),
+    absolute: emptyAgeFields(),
+    composite: emptyAgeFields(),
+  }
+
+  const dateMethod = toDatingMethod(editData.date_meth)
+  if (!dateMethod) return drafts
+
+  return { ...drafts, [dateMethod]: getAgeFields(editData) }
+}
 
 export const AgeTab = () => {
   const { textField, radioSelection, dropdown, bigTextField, editData, setEditData, data } =
     useDetailContext<LocalityDetailsType>()
+  const [ageDraftsByMethod, setAgeDraftsByMethod] = useState<AgeDraftsByMethod>(() => initializeDrafts(editData))
 
   const { data: bfaMinData, isFetching: bfaMinFetching } = useGetTimeUnitDetailsQuery(editData.bfa_min || skipToken)
   const { data: bfaMaxData, isFetching: bfaMaxFetching } = useGetTimeUnitDetailsQuery(editData.bfa_max || skipToken)
 
+  useEffect(() => {
+    setAgeDraftsByMethod(initializeDrafts(makeEditData(data)))
+  }, [data])
+
   const minTimeUnitDisplay = data.bfa_min_time_unit?.tu_display_name
   const maxTimeUnitDisplay = data.bfa_max_time_unit?.tu_display_name
 
@@ -50,19 +105,24 @@ export const AgeTab = () => {
   ]
 
   const handleDateMethChange = (value: number | string | boolean) => {
-    // this is to satisfy type requirements of handleSetEditData
-    if (typeof value !== 'string') return
+    const nextDateMethod = toDatingMethod(value)
+    if (!nextDateMethod) return
+
+    const currentDateMethod = toDatingMethod(editData.date_meth)
+    const nextDrafts = { ...ageDraftsByMethod }
+
+    if (currentDateMethod) {
+      nextDrafts[currentDateMethod] = getAgeFields(editData)
+    }
+
+    const restoredFields = nextDrafts[nextDateMethod] ?? emptyAgeFields()
+
+    setAgeDraftsByMethod(nextDrafts)
+
     setEditData({
       ...editData,
-      date_meth: value,
-      min_age: undefined,
-      bfa_min_abs: '',
-      bfa_min: '',
-      frac_min: '',
-      max_age: undefined,
-      bfa_max_abs: '',
-      bfa_max: '',
-      frac_max: '',
+      date_meth: nextDateMethod,
+      ...restoredFields,
     })
   }
 
diff --git a/frontend/src/shared/validators/locality.ts b/frontend/src/shared/validators/locality.ts
index d3720c64..0e00e89f 100755
--- a/frontend/src/shared/validators/locality.ts
+++ b/frontend/src/shared/validators/locality.ts
@@ -29,12 +29,21 @@ export const validateLocality = (
   editData: EditDataType<LocalityDetailsType>,
   fieldName: keyof EditDataType<LocalityDetailsType>
 ) => {
+  const isAbsoluteDatingMethod = editData.date_meth === 'absolute'
+  const isTimeUnitDatingMethod = editData.date_meth === 'time_unit'
+  const isCompositeDatingMethod = editData.date_meth === 'composite'
+
+  const minUsesAbsoluteBasis = !!editData.bfa_min_abs
+  const minUsesTimeUnitBasis = !!editData.bfa_min
+  const maxUsesAbsoluteBasis = !!editData.bfa_max_abs
+  const maxUsesTimeUnitBasis = !!editData.bfa_max
+
   const compositeDatingMethodNoBases =
-    editData.date_meth === 'composite' &&
-    !editData.bfa_min &&
-    !editData.bfa_min_abs &&
-    !editData.bfa_max &&
-    !editData.bfa_max_abs
+    isCompositeDatingMethod &&
+    !minUsesTimeUnitBasis &&
+    !minUsesAbsoluteBasis &&
+    !maxUsesTimeUnitBasis &&
+    !maxUsesAbsoluteBasis
 
   const compositeDatingMethodRequiredText = 'One age row must follow the rules for Absolute, the other for Time Unit'
 
@@ -65,8 +74,7 @@ export const validateLocality = (
     bfa_min_abs: {
       name: 'Basis for age (Absolute, min)',
       required: () => {
-        if (editData.date_meth === 'absolute' || (editData.date_meth === 'composite' && !!editData.bfa_max))
-          return 'This field is required'
+        if (isAbsoluteDatingMethod || (isCompositeDatingMethod && maxUsesTimeUnitBasis)) return 'This field is required'
         if (compositeDatingMethodNoBases) return compositeDatingMethodRequiredText
         return
       },
@@ -74,8 +82,7 @@ export const validateLocality = (
     bfa_max_abs: {
       name: 'Basis for age (Absolute, max)',
       required: () => {
-        if (editData.date_meth === 'absolute' || (editData.date_meth === 'composite' && !!editData.bfa_min))
-          return 'This field is required'
+        if (isAbsoluteDatingMethod || (isCompositeDatingMethod && minUsesTimeUnitBasis)) return 'This field is required'
         if (compositeDatingMethodNoBases) return compositeDatingMethodRequiredText
         return
       },
@@ -83,8 +90,7 @@ export const validateLocality = (
     bfa_min: {
       name: 'Basis for age (Time unit, min)',
       required: () => {
-        if (editData.date_meth === 'time_unit' || (editData.date_meth === 'composite' && !!editData.bfa_max_abs))
-          return 'This field is required'
+        if (isTimeUnitDatingMethod || (isCompositeDatingMethod && maxUsesAbsoluteBasis)) return 'This field is required'
         if (compositeDatingMethodNoBases) return compositeDatingMethodRequiredText
         return
       },
@@ -92,8 +98,7 @@ export const validateLocality = (
     bfa_max: {
       name: 'Basis for age (Time unit, max)',
       required: () => {
-        if (editData.date_meth === 'time_unit' || (editData.date_meth === 'composite' && !!editData.bfa_min_abs))
-          return 'This field is required'
+        if (isTimeUnitDatingMethod || (isCompositeDatingMethod && minUsesAbsoluteBasis)) return 'This field is required'
         if (compositeDatingMethodNoBases) return compositeDatingMethodRequiredText
         return
       },