Not directly for a site-site (IPsec) VPN. If it is an active VPN, you can use the command:
show crypto isakmp sa detail
That will show you the lifetime and lifetime remaining.
However the VPN, as represented by the Security Association or "sa" will renew itself when the sa expires as long as interesting traffic is being presented to one peer or the other.
A better method is to be gathering the syslog messages that are generated when a VPN establishes.
If you are asking about a remote access (user) SSL VPN, you can see the age of the current connections with the command:
show vpn-sessiondb anyconnect
If you want to pare down the output, tell it to only gives you lines with the username and login time, as follows:
show vpn-sessiondb anyconnect | i User|Login
