This is happening on multiple Zen Cart sites. All seem to be ZC 1.5.8 and PHP 8.x

PHP Fatal error: Uncaught IntlException: datefmt_create: invalid locale: U_ILLEGAL_ARGUMENT_ERROR in /XXXXXX/includes/classes/zcDate.php:87

I saw a thread about this error and PHP 8.3 on GitHub, but see no mention in this forum.