The time at which an user action occurred. This type has the 2 following special values:
0: the action doesn't involve any user action. Clients SHOULD avoid stealing focus when presenting the channel.
MAX_INT64: clients SHOULD behave as though the user action happened at the current time, e.g. a client MAY request that its window gains focus.
This can be used by clients that can't know the X server time like command line applications for example.
For all the other values it corresponds to the time of the user action. Clients SHOULD use this for focus-stealing prevention, if applicable. Note that the time is dependant on the local environment and so is not necessarily a wall-clock time. For example in an X environment it's expected to be the X timestamp of events. This corresponds to the _NET_WM_USER_TIME property in EWMH.