The juridical force of time forms a critical, but hitherto unexplored part of Hugo Grotius’s discourse on the justice of war and peace. Grotius defines war as a span of time in which disputed rights and armed conflicts between states are examined in reference to temporal coordinates. This method allows him to adjust otherwise static laws to meet the demands of times and spaces in an increasingly expanded world. In doing so, Grotius is also able to reconcile multiple layers of laws in a temporal framework, which suspends one layer of law, to be revived at later times. Finally, cautious in the use of the language of time, Grotius admits both that right demands immediacy, and that justice suffers delays. By this nexus of delay (mora) and emergency (necessitas), Grotius warns against the abuse of ‘time’ as a legal concept to justify unlawful claims, which still rings with alarm today.