Dark matter may be generated by new physics at the TeV scale during an early matter dominated era that ends at temperature much below the TeV scale. Compared to conventional radiation dominated results, yields from both Freeze-Out and Freeze-In processes are greatly suppressed by dilution from entropy production, making Freeze-Out less plausible while allowing successful Freeze-In with a much larger coupling strength. For a large fraction of the relevant cosmological parameter space, the decay rate required to produce the observed dark matter abundance leads to displaced signatures at LHC and future colliders.