Credential Issuer Metadata value_type for dates

[bruno-zimmermann-bit]

For holders and verifiers to being able to parse dates dynamically in credentials it would be beneficial to have the date format encoded in the metadata.

Have there been any considerations for how to handle date and datetime values?

I would see a solution to use the RFC3339 for value_type.

Example Issuer Metadata

"credentialSubject": {
        "birthday": {
                "value_type": "full-date"
        },
        "graduation_year": {
                "value_type": "date-fullyear"
        }
}

Example Credential Data

"credentialSubject": {
        "birthday": "1970-01-01"
        "graduation_year": "2023"
}