Add ext-calendar as requirement in composer.json
MODIFY
composer.json
composer.json
"type": "project",
"require": {
"php": "^7.4|^8.0",
+ "ext-calendar": "*",
"doctrine/dbal": "^2.8",
"fideloper/proxy": "^4.0",
"fruitcake/laravel-cors": "^1.0",

MODIFY
composer.lock
composer.lock
"Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
"This file is @generated automatically"
],
- "content-hash": "16d148095551ee3835bbc68ffa65d86c",
+ "content-hash": "648976cf6087cfbbc445a1cc9dbb074a",
"packages": [
{
"name": "asm89/stack-cors",
"prefer-stable": false,
"prefer-lowest": false,
"platform": {
- "php": "^7.4|^8.0"
+ "php": "^7.4|^8.0",
+ "ext-calendar": "*"
},
"platform-dev": [],
- "plugin-api-version": "1.1.0"
+ "plugin-api-version": "2.2.0"
}

Add ext-calendar as requirement in composer.json