Easily check if a TLS Certificate is still valid and when it is about to expire

curl https://www.certchek.io/www.yourdomain.com/json

{
    "fqdn": "www.certcheck.io",
    "startdate": {
        "year": 2021,
        "month": 3,
        "day": 1,
        "date": "2021-03-01",
        "epoch": 1614556800,
        "days_since_startdate": 13
    },
    "enddate": {
        "year": 2021,
        "month": 5,
        "day": 30,
        "date": "2021-05-30",
        "epoch": 1622332800,
        "days_before_enddate": 77
    },
    "issuer": "Country: US, Organization: Let's Encrypt, Common Name: R3",
    "subject": "Common Name: *.watuppa.it",
    "san": "*.watuppa.it, watuppa.it"
}