The event will become true at 00:00 of 1st, 3rd and last week of a month and will remain true during all the week. 
				
					{
    "blockOptions": {
        "method": {
        "args": {
            "type": "type",
            "weeks": "weeks"
        },
        "name": "isDate"
        }
    },
    "blockType": "when",
    "fields": [
        {
            "name": "type",
            "type": "string",
            "value": "weeks"
        },
        {
            "name": "weeks",
            "type": "int_array",
            "value": [1, 3, -1]
        }
    ]
}