MonthPicker

MonthPicker is the grid-based month-selection subsystem used directly or as part of the calendar family.

Root Props

Prop	Type	Default
`year`	`string`	—
Year whose months are shown, given as a `YYYY-MM-DD` string of any day in it. Defaults to the current year.
`calendar`	`CalendarSystem`	`gregorianCalendar`
Calendar system the months belong to — it defines how many months a year has. Defaults to the Gregorian calendar.
`locale`	`string`	`getDefaultLocale()`
BCP 47 locale of the month names, e.g. `de-DE`. Defaults to the locale of the runtime, like `Intl`.
`size`	`DataGridPickerSize`	`'xs'`
Controls the item’s visual size. Useful for adapting the picker to compact or large layouts.
`variant`	`DataGridPickerVariant`	—
Visual appearance preset for the picker.
`selection`	`S`	`'single'`
Selection mode. `'single'` — only one cell can be selected at a time; `'multiple'` — independent multi-selection (toggle per cell); `'range'` — range selection between two points (Shift + arrows or pointer drag)
`disabled`	`DataGridDisabled<string>`	—
Predicate or map of disabled cells. Can be: a function `(key) => boolean`; an array of disabled keys; a single key. Disabled cells cannot be selected or focused.
`excludeDisabled`	`boolean`	—
—
`expandable`	`boolean`	`true`
Enables expanding selection ranges (Shift + Arrow or mouse drag).
`defaultActive`	`string`	—
Uncontrolled initial active cell.
`active`	`string`	—
Controlled active cell.
`selected`	`S extends "single" ? string \| null : string[]`	—
Controlled selected cells. In `'single'` mode `null` means controlled with nothing selected.
`defaultSelected`	`S extends "single" ? string : string[]`	—
Uncontrolled initially selected cells.
`from`	`string`	—
Range boundaries. If provided, limits selection to cells between `from` and `to` based on the `compare` function.
`to`	`string`	—
—
`resolveRange`	`(start: DataGridResolveValue<K>, end: DataGridResolveValue<K>, grid: Grid<HTMLElement, K>) => K[]`	—
Custom range resolution logic for `selection="range"`. Given start and end values, returns the list of keys forming the range.
`equals`	`(start: K \| undefined, end: K \| undefined) => boolean`	—
Custom equality comparator for comparing two cell keys. Defaults to strict equality (`===`).
`compare`	`(a: K, b: K) => -1 \| 0 \| 1`	—
Custom ordering comparator for comparing two cell keys. Should return `-1`, `0`, or `1`.
`onSelectCell`	`(value: S extends 'single' ? K : K[]) => void`	—
Fires when the user selects cell. Receives the list of selected cell keys.
`onChangeActive`	`(active: K) => void`	—
Fires when the active (focused) cell changes.
`ref`	`Ref<HTMLDivElement>`	—
Ref to the grid’s root element.
`apiRef`	`Ref<DataGridApiRef<string>>`	—
Ref to the grid’s imperative API. Exposes low-level structures for advanced scenarios: `grid` — matrix navigation helper; `keyMap` — Map`<K, [row, col]>` for fast lookups
`wrap`	`DataGridWrap`	—
Navigation wrap mode. 'horizontal' — wrap across columns within the same row; 'vertical' — wrap across rows within the same column; 'both' — enable both behaviors; undefined — no wrapping
`exclude`	`DataGridExclude<string>`	—
Exclude cells from focus traversal. Can be: a single key; an array of keys; a predicate `(key) => boolean`
`rowDelta`	`number`	—
Page navigation row step for PageUp/PageDown. `undefined` — jump to the first/last row; `number` — move by N rows relative to the current row
`onArrow`	`(e: KeyboardEvent<HTMLDivElement>, node: MatrixNode<HTMLElement, K>, prevNode: MatrixNode<HTMLElement, K>) => void`	—
Fires on each Arrow navigation step after focus changes

Also accepts all <div> attributes.

Child Parts

MonthPickerLayout
MonthPickerRowGroup
MonthPickerRow
MonthPickerItem
MonthPickerCell

`MonthPickerItem`

Prop	Type	Default
`range`	`DataGridPickerItemRangePosition`	—
Optional visual indicator of the cell’s position within a range. One of: `"start" \| "between" \| "end"`. If not provided, the component automatically derives it based on selection context.
`size`	`DataGridPickerSize`	—
Controls the item’s visual size. Useful for adapting the picker to compact or large layouts.
`value`	`DataGridCellKey`	—
Logical value associated with this grid cell. Used as the cell’s unique selection key.
`variant`	`DataGridPickerVariant`	—
Visual appearance preset for the picker.
`disabled`	`boolean`	—
Disables click and keyboard selection. Overrides value from root DataGrid
`ref`	`Ref<HTMLDivElement>`	—
External ref to the cell root element. Will be merged with the internal `itemRef([row, col], key)` registration when the cell is not excluded.
`col`required	`number`	—
Column index of the cell (0-based). Used together with row index from the row context to form grid coordinates: `[row, col]`.
`asChild`	`boolean`	`false`
When `true`, renders children via `Slot` and forwards props/refs to the child element instead of using a native `<div>`.
`excluded`	`boolean`	—
Exclude cells from focus traversal. Overrides value from root DataGrid

Also accepts all <div> attributes.

`MonthPickerCell`

Prop	Type	Default
`size`	`DataGridPickerSize`	—
Controls the item’s visual size. Useful for adapting the picker to compact or large layouts.
`range`	`DataGridPickerItemRangePosition`	—
Optional visual indicator of the cell’s position within a range. One of: `"start" \| "between" \| "end"`. If not provided, the component automatically derives it based on selection context.
`variant`	`DataGridPickerVariant`	—
Visual appearance preset for the picker.
`disabled`	`boolean`	—
Disables click and keyboard selection. Overrides value from root DataGrid
`ref`	`Ref<HTMLDivElement>`	—
External ref to the cell root element. Will be merged with the internal `itemRef([row, col], key)` registration when the cell is not excluded.
`asChild`	`boolean`	`false`
When `true`, renders children via `Slot` and forwards props/refs to the child element instead of using a native `<div>`.
`excluded`	`boolean`	—
Exclude cells from focus traversal. Overrides value from root DataGrid

Also accepts all <div> attributes.

`MonthPickerRow`

Prop	Type	Default
`row`required	`number`	—
Zero-based row index for all descendant cells. Provided to descendants via context.

Also accepts all <div> attributes.

`MonthPickerRowGroup`

Prop	Type	Default
`scope`	`DataGridScope`	—
The `scope` prop is required and identifies the logical group of cells rendered by this row group. When used with `DataGridIndexedSnapScroller`, the scope usually matches the current index or page. Providing a scope allows the DataGrid to restore focus to the first available cell when the index changes and new cells are rendered.

Also accepts all <div> attributes.

`MonthPickerLayout`

Prop	Type	Default
`children`required	`ReactNode`	—
Template of a month cell, rendered once for every month of the year. Read the month with `useMonthPickerCellContext()`; usually `<MonthPickerCell />`.
`cols`	`number`	`3`
Number of columns; rows are added as needed for all months of the year.
`locale`	`string`	—
Locale used for formatting month names. Defaults to the locale of the picker.
`format`	`Intl.DateTimeFormatOptions['month']`	`'long'`
Month display format (from `Intl.DateTimeFormatOptions`).
`scope`	`DataGridScope`	—
The `scope` prop is required and identifies the logical group of cells rendered by this row group. When used with `DataGridIndexedSnapScroller`, the scope usually matches the current index or page. Providing a scope allows the DataGrid to restore focus to the first available cell when the index changes and new cells are rendered.

Also accepts all <div> attributes.

Types

MonthPickerProps
MonthPickerLayoutProps
MonthPickerRowGroupProps
MonthPickerRowProps
MonthPickerItemProps
MonthPickerCellProps
MonthPickerCellContextData

State Model

Selection and bounds behavior are inherited from DataGridPicker.
Months are keyed by their first day as a YYYY-MM-DD string; selected, from, to, and disabled use the same strings.
The root provides the visible year (its first day) and calendar through useMonthPickerContext.
createMonthPickerGrid({ year, calendar, cols }) derives the rows from the months of the year: 12, or 13 in Hebrew leap years.
MonthPickerLayout formats labels with Intl.DateTimeFormat in the picker's calendar system.
Children of MonthPickerLayout are the template of a cell, rendered once per month inside a cell context. The children are required, usually <MonthPickerCell />, which shows the formatted label.
useMonthPickerCellContext() returns { col, date, fields, label }; date is the first day of the month. Take month numbers from label or fields, never from the ISO date string.
locale and calendar are root props; the layouts accept their own locale override.