rubygemで証明書有効期限ぎれ

Unable to download data from https://rubygems.org/ - SSL_connect retur
ned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed (
https://api.rubygems.org/latest_specs.4.8.gz)
https://raw.githubusercontent.com/rubygems/rubygems/master/lib/rubygems/ssl_certs/AddTrustExternalCARoot-2048.pem
....libruby2.*.*rubygemsssl_certs