During evolution, a wide range of organisms from cyanobacteria to humans have adapted to the day-night cycle, caused by the earth’s rotational movements, by developing an endogenous timing system – a circadian clock – that allows synchronization of metabolism, physiology and behaviour with the environment and that also may modulate seasonal responses. Our current molecular understanding of biological rhythms and clocks is largely restricted to circadian and seasonal rhythms in land model species such as the fruit fly, the mouse or the thale cress. In marine organisms in general, little is known about the principles of endogenous clocks and how these clocks interact with environmental cycles. Marine ecosystems are currently experiencing rapid anthropogenic climatic changes. In particular, polar and sub-polar latitudes comprising the fastest warming regions on the planet with profound impacts on the marine environment. The overall aim of the Helmholtz Virtual Institute (HVI) PolarTime is to create a center of excellence of international standing to study the principles, interactions and evolution of endogenous biological rhythms and clocks in polar pelagic organisms. Emphasis will be placed on invertebrate key species who’s biology is so pervasive as to dictate ecosystem functioning. The Southern ocean key species Antarctic krill, Euphausia superba, will act as model organism to study the endogenous clock machinery and its effect on daily and seasonal life-cycle functions. The results will act as solid basis to study and understand the mechanisms of temporal synchronization of other key polar pelagic organisms. Embedded modelling studies will enable us to understand and predict how the ongoing environmental changes will impact the clock machinery and consequently the life cycle of key species and hence the whole polar marine ecosystem.