The deadzone is the period of time in each tick when the hypergates are closed. Players are unable to engage their hyper engines to move from one sector to another during this time. The name "deadzone" is derived from the fact that most deaths occur during this period (as players focus their moves at the time when their prey cannot escape). The deadzone is characterised by the timer turning red.
In betas the deadzone usually spans the first 5 minutes (300 seconds) and last 15 minutes (900 seconds) of every tick. The deadzone for frantics is usually the first 2 minutes (120 seconds) and last 1 minute (60 seconds) of each tick.
The deadzone for the current game is the first 5 minutes and the last 15 minutes of each tick. If these figures are out of date you can update them here.