The calendar system defines how rules, dates and times are to be interpreted. Currently only the value "Gregorian" is supported, referring to the Gregorian calendar scale. If this element is not present in its normal context, then the value "Gregorian" MUST be assumed. Provides the UTC date and time when a substantive change was made to the timezone data. Provides the UTC date and time that the timezone data was last modified. Defines one or more localized names that are used when a timezone identifier needs to be presented to a user. The xml:lang attribute is used to indicate the language associated with each value. If multiple names are provided for the same locale the first is considered the preferred name. The onset element defines the local time at which the observance takes effect. The text value is the identifier of the timezone being referred to. The utc-offset-from element defines the UTC offset in hours and minutes before the start of this observance. The utc-offset-to element defines the UTC offset in hours and minutes at and after the start of this observance. Defines alternative identifiers that can be used for the timezone. This feature allows mapping of old identifiers onto new. This defines the name, type and characteristics of an operation parameter. The element used as the container for information defining an operation and its parameters. . The root (top-level) element used as the container for capabilities information. This defines the element that provides summary information for a timezone in the timezones list. This defines the root (top-level) element used as the container for a timezone listing. In an expanded timezone, the observance element specifies a single timezone observance. This element specifies expanded timezone data for the range specified in a request. This defines the root (top-level) element used as the container for expanded timezone data.