Yes, every block has a timestamp in it and the difficulty adjustment algorithm looks at these timestamps when deciding how to adjust difficulty.
Nodes trust the timestamp in a given block based on pre-defined rules:
A timestamp is accepted as valid if it is greater than the median timestamp of previous 11 blocks, and less than the network-adjusted time + 2 hours. "Network-adjusted time" is the median of the timestamps returned by all nodes connected to you.
https://en.bitcoin.it/wiki/Block_timestamp