A special transaction where the recipient can only spend the funds after a future date, as set by the sender.
Unlock time allows you to send a transaction to someone, such that they can not spend it until after a certain number of blocks, or until a certain time.
Note that this works differently than Bitcoin’s nLockTime, in which the transaction is not valid until the given time.
In Haven unlock times also have variable unlock times depending on the transaction type. The basics are covered here:
Transfers= 10 blocks (~20 mins)
XHV<>xUSD= user defined variable depending on fee selected
xUSD<>xAssets= 10 blocks (~20 mins)