In calendar.xml CLDR defines "islamic" and "islamicc" for the astronomical and algorithmic variants respectively.
This is a request to consider adding more Islamic calendar variants or enhance the calendar naming scheme to identify the Islamic calendar variants unambiguously.
The background of this request is that JSR-310 must identify the Islamic dates correctly and this requires identifying the specific variants and distinctively identify each of them.
For example, the Umm Al-Qura calendar and Microsoft's Islamic calendar implementation with the Kuwaiti algorithm are both algorithmic but they are different, so the date information is not interchangeable under "islamicc" between different variants. A date in one variant may correspond to a different date in another variant. So, in terms of ensuring correct exchange of Islamic date information, not identifying the precise variants in the CLDR name space falls short of the use case expectation. We anticipate Islamic end users might have their preferred Islamic calendar variant set in their user profile, or an application may be supporting different variants in producing some output with Islamic date information.
One approach to resolve this variant identification problem is appending a subtag to islamicc/islamic; for example: