A single calendar month, optimized for a given locale
Demo: A default representation for the current month in browser's default locale


Given a reference date property, this component will show a calendar representation of that month. To the extent possible, this representation is sensitive to a specified locale: the names of the months and days of the week will be in the appropriate language, and the day(s) associated with the weekend in that locale will also be indicated.

International support

All of the Elix calendar components attempt to provide full international support to the extent currently possible in the user's web browser. This includes being able to automatically show localized text strings for the desired language, as well as applying the desired region's cultural preferences for calendar layout.

Demo: English/U.S.: Weeks start on Sunday
Demo: English/Great Britain: Weeks start on Monday
Demo: French/France: Month and day names in French
Demo: Japanese/Japan: Month and day names in Japanese
Demo: Arabic/Kuwait: Weeks start on Saturday, weekend is Friday–Saturday
Demo: Hindi/India: Weekend is just Sunday

The precise set of supported locales may vary from browser to browser.

Demo: Calendars for the locales your browser supports


Like all complex Elix components, CalendarMonth and its associated calendar components can be extensively customized.

Demo: CalendarMonth showing custom data: here, the phase of the moon

The above calendar has been customized by defining a custom element that extends CalendarDay to show the phase of the moon on that day. This custom element is then used to fill the Day role on CalendarMonth. CalendarMonth will instantiate that custom element class for each day of the month and pass in the date that the element should show. The custom element can then perform whatever calculations and rendering logic it needs to show the appropriate data for that date.


Ancestry: CalendarMonth → ReactiveElement → HTMLElement

Built with mixins AttributeMarshallingMixin, CalendarElementMixin, ReactiveMixin, RenderUpdatesMixin, and ShadowTemplateMixin.

By default, this uses these elements in the following roles:

$ property

A convenient shortcut for looking up an element by ID in the component's Shadow DOM subtree.

Example: if component's template contains a shadow element <button id="foo">, you can use the reference this.$.foo to obtain the corresponding button in the component instance's shadow tree. The $ function is simply a shorthand for getElementById, so this.$.foo is the same as this.shadowRoot.getElementById('foo').

Type: object

Defined by ShadowTemplateMixin

date property

The date that should be shown by the element. For elements that show a range of dates (a month, a week, etc.), the referenced date will be included in the range.

This property can be set as a string, which will be parsed and converted to a JavaScript Date.

If not specified, the default date value is the current date.

Type: Date|string

Defined by CalendarElementMixin

dayElementForDate(date) method

Returns the day element corresponding to the given date, or null if the date falls outside the range currently covered by this calendar.


  • date: Datethe date to search for

Returns: Elementnull

dayRole property

The class, tag, or template used for the seven days of the week.

Type: function|string|HTMLTemplateElement

Default: CalendarDay

days property

Returns the day elements contained by this calendar. Note that this may include days from the previous/next month that fall in the same week as the first/last day of the present month.

Type: Array.

daysOfWeekFormat property

The format used to render the day names in the week days header.

Type: 'long'|'narrow'|'short'

Default: 'short'

defaultState property

The default state for the component. This can be extended by mixins and classes to provide additional default state.

Type: object

Defined by ReactiveMixin

locale property

A string that identifies a language and a region using a BCP 47 language tag. This is the same format used by to identify a locale in the standard Intl internationalization API. See the locales argument documentation for details.

Calendar elements are region-sensitive, so language alone is insufficient. Accordingly, the locale should identify at least a language and a region. Examples: "en-US" identifies US English, while "en-GB" identifies English in Great Britain. The use of "en" on its own would be insufficient.

Type: string

Defined by CalendarElementMixin

refineState(state) method

Apply changes to a proposed new state for the component to enforce necessary consistency between state members. See Refining state for details.


  • state: objecta proposed new state for the component

Returns: boolean - true if the state is already acceptable as it is

Defined by ReactiveMixin

render() method

Render the component to the DOM.

This method does nothing if the state has not changed since the last render call.

This method invokes all internal render methods. It then invoked componentDidMount (for first render) or componentDidUpdate (for subsequent renders).

Defined by ReactiveMixin

setState(changes) method

Update the component's state by merging the specified changes on top of the existing state. If the component is connected to the document, and the new state has changed, this returns a promise to asynchronously render the component. Otherwise, this returns a resolved promise.


  • changes: objectthe changes to apply to the element's state

Returns: Promise - resolves when the new state has been rendered

Defined by ReactiveMixin

shouldComponentUpdate(nextState) method

Return true if the component should update.

The default implementation does a shallow check of property values like React's PureComponent. This seems adequate for most web components. You can override this to always return true (like React's base Component class), or to perform more specific, deeper checks for changes in state.


  • nextState: objectthe proposed new state for the element

Returns: boolean - true if the component should update (rerender)

Defined by ReactiveMixin

state property

The component's current state. The returned state object is immutable. To update it, invoke setState.

Type: object

Defined by ReactiveMixin

updates property

The attributes and properies that should be applied to the component on render. By default, this is an empty plain object. Your mixin or component can extend this to identify the properties to set on the host element or elements in the shadow subtree.

Type: object

Defined by RenderUpdatesMixin

weekElementForDate(date) method

Returns the week element for the week containing the given date, or null if the date falls outside the calendar's range.


  • date: Datethe date to search for

Returns: Elementnull

weekRole property

The class, tag, or template used for the weeks of the month.

Type: function|string|HTMLTemplateElement

Default: CalendarWeek

weeks property

Returns the set of week elements used by the calendar.

Type: Array.