WordPress/wp-includes/blocks/calendar/block.json

{
	"apiVersion": 2,
	"name": "core/calendar",
	"category": "widgets",
	"attributes": {
		"month": {
			"type": "integer"
		},
		"year": {
			"type": "integer"
		}
	},
	"supports": {
		"align": true
	}
}