When holding at a fix and instructions are received specifying the time of departure from the fix to continue with the clearance previously received or to commence the approach, the pilot should adjust his flight path within the limits of the established holding pattern in order to leave the fix at the exact time specified.
Departing the holding fix, normal speed is to be resumed with respect to other governing speed requirements such as terminal area speed limits, maximum initial approach speeds, specific ATC requests, etc.
Source: ICAO
See also:
Approaching Holding fix
Entry into the Holding
Holding pattern shape and terminology
Standard limitations for Speed, Rate of turn and Timing (Holding)
Flying the Holding pattern – Wind correction
Leaving the Holding pattern
Protected airspace (Holding)