Why am I not able to install Android SDK?

I installed android sdk. When I click the android sdk manager. Then the the following error message is displayed in an alert box

Failed to fetch URL https://dl-ssl.google.com/android/repository/repository.xml, reason: sun. Security. Validator. ValidatorException: PKIX path validation failed: java.security.cert.certPathValidatorException: ti开发者_运维百科mestamp check failed

Please help me to solve the issues.

The certificate of this site seems valid to me. You should check your system's date and time settings and maybe correct them. If this is not working, you could try to use a non-SSL connection with http:// like Kenny already mentioned in his comment.

Try to use http instead of https in the settings

Please follow the link. Installing the Android SDK

Well, to be clear, I got the trivial hint from the discussion about how to deal with newbies, and after that and reading the the error message more carefully the solution was obvious: My (virtual) machine had an OLD TIME. After setting the time correctly, it worked.