Intl.DateTimeFormat.prototype.resolvedOptions()

None.

A new object with properties reflecting the options computed during the initialization of the given Intl.DateTimeFormat object. The object has the following properties, in the order they are listed:

locale

The BCP 47 language tag for the locale actually used. Only the ca, hc, and nu Unicode extension keys may be included in the output.

calendar

One of the supported calendar types, reflecting the value provided for this property in the options argument or the ca Unicode extension key. The default is locale dependent.

numberingSystem

One of the supported numbering system types, reflecting the value provided for this property in the options argument or the nu Unicode extension key. The default is locale dependent.

timeZone

One of the IANA time zone names, reflecting the value provided for this property in the options argument. The default is the runtime's default time zone; should never be undefined.

Note: While the IANA database changes from time to time, the Unicode CLDR database (which browsers use) keeps old time zone names for stability purposes. All browsers canonicalize time zone names, but in different directions. For example, new Intl.DateTimeFormat("en-US", { timeZone: "Europe/Kiev" }).resolvedOptions().timeZone and new Intl.DateTimeFormat("en-US", { timeZone: "Europe/Kyiv" }).resolvedOptions().timeZone will return the same string in the same browser, but maybe different strings in different browsers. See Intl.Locale.prototype.getTimeZones for more information.

hourCycle

The value provided for this property in the options argument, or provided in the Unicode extension key "hc", with default filled in as needed. Only present if the options argument included hour or timeStyle.

hour12

The value provided for this property in the options argument, or computed from the hourCycle property. Only present if the options argument included hour or timeStyle.

weekday, era, year, month, day, dayPeriod, hour, minute, second, fractionalSecondDigits, timeZoneName

The values resulting from format matching between the corresponding properties in the options argument and the available combinations and representations for date-time formatting in the selected locale. Some of these properties may not be present, indicating that the corresponding components will not be represented in formatted output. If the dateStyle or timeStyle shortcuts were used in options, these individual component properties will never be present.

dateStyle, timeStyle

The values provided for these properties in the options argument, if any.

Although dateStyle and timeStyle are shortcuts for individual date and time component styles, the exact (locale dependent) component styles they resolve to are not included in the resolved options. This ensures the result of resolvedOptions() can be passed directly to the Intl.DateTimeFormat() constructor (because an options object with both dateStyle or timeStyle and individual date or time component styles is not valid).

The Intl.DateTimeFormat constructor without any options uses the current system settings. You can use resolvedOptions() to get the user's current time zone and locale's preferred calendar and numbering system:

const systemOptions = new Intl.DateTimeFormat().resolvedOptions();
systemOptions.timeZone; // e.g., "Europe/Brussels" or "Asia/Riyadh"
systemOptions.calendar; // e.g., "gregory" or "islamic-umalqura"
systemOptions.numberingSystem; // e.g., "latn" or "arab"
systemOptions.locale; // e.g., "nl-BE" or "ar-SA"

• Intl.DateTimeFormat