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.

The core grid of dates in CalendarMonth is provided by CalendarDays. To this, the component adds instances of CalendarMonthYearHeader and CalendarDayNamesHeader.

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, and ShadowTemplateMixin.

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

Extended by class CalendarMonthNavigator.

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

date-changed event

Raised when the date property changes.

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 to create the day elements.

Type: (component class constructor)|HTMLTemplateElement|string

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.

The allowable formats are the same as the weekday formats in Intl.DateTimeFormat.

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

Default: 'short'

[internal.defaultState] property

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

Type: State

Defined by ReactiveMixin

[internal.ids] 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[internal.ids].foo to obtain the corresponding button in the component instance's shadow tree. The ids property is simply a shorthand for getElementById, so this[internal.ids].foo is the same as this.shadowRoot.getElementById('foo').

Type: object

Defined by ShadowTemplateMixin

[internal.render](changed) method

Render the indicated changes in state to the DOM.

The default implementation of this method does nothing. Override this method in your component to update your component's host element and any shadow elements to reflect the component's new state. See the rendering example.

Be sure to call super in your method implementation so that your component's base classes and mixins have a chance to perform their own render work.


  • changed: objectdictionary of flags indicating which state members have changed since the last render

Defined by ReactiveMixin

[internal.renderChanges]() method

Render any pending component changes to the DOM.

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

ReactiveMixin will invoke this method following a setState call; you should not need to invoke this method yourself.

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

Defined by ReactiveMixin

[internal.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

[internal.state] property

The component's current state.

The returned state object is immutable. To update it, invoke internal.setState.

It's extremely useful to be able to inspect component state while debugging. If you append ?elixdebug=true to a page's URL, then ReactiveMixin will conditionally expose a public state property that returns the component's state. You can then access the state in your browser's debug console.

Type: State

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

monthFormat property

The format used to render the month name.

The allowable formats are the same as the month formats in Intl.DateTimeFormat.

Type: 'numeric'|'2-digit'|'long'|'short'|'narrow'

Default: 'long'

yearFormat property

The format used to render the year.

The allowable formats are the same as the year formats in Intl.DateTimeFormat.

Type: 'numeric'|'2-digit'

Default: 'numeric'