This alias exists because the name "Gregorian" is too long to be used in a locale identifier, i.e. "en-u-ca-gregorian" is invalid. Aliases for calendars are defined here: https://github.com/unicode-org/cldr-json/blob/main/cldr-json/cldr-bcp47/bcp47/calendar.json However, CLDR version 40 neglected to actually include the cldr-bcp47 package in its release, so we don't have access to this data. So for now hard-code this alias so that JavaScript can actually access it. See: https://unicode-org.atlassian.net/browse/CLDR-15158
Similar to number formatting, the data for date-time formatting will be located in its own generated file. This extracts the cldr-dates package from the CLDR and sets up the generator plumbing to create the date-time data files.
