An insulation-time determining device for a thermally insulated container with a latent heat accumulator includes energy-calculating equipment for calculating the amount of thermal energy stored in the latent heat accumulator from at least one status parameter of the thermally insulated container or the interior thereof as well as display equipment for displaying the calculated amount of stored thermal energy or a value correlated therewith. The insulation-time determining device also includes insulation-time calculating equipment to calculate a maximum insulation time provided with a safety correction factor of the thermally insulated container from the calculated amount of stored thermal energy or a value correlated therewith and a specified external temperature progression outside the thermally insulated container, during which maximum insulation time a specified temperature range is neither fallen below nor exceeded in the interior of the thermally insulated container.