# cf.tls\_client\_auth.cert\_not\_before

`cf.tls_client_auth.cert_not_before` String

The certificate in the request is not valid before this date.

This field is only filled in if the request includes a client certificate for [mTLS authentication](https://developers.cloudflare.com/ssl/client-certificates/enable-mtls/).

Example value:

```txt
"Mar 21 13:35:00 2022 GMT"
```

Categories:

* Request
* mTLS
