We investigated the time dependence of the magnetic configuration at the mixed magnetic magnetostructural transition in Mn3SnC. The nonergodic nature of the transition involves the stabilization of a final magnetic configuration that involves additional AF ordering which is not present when the transition is initiated and develops only in time. We show the presence of the nonergodicity over a time scale of about 1 hour by field and time-dependent magnetization studies. Two characteristic times related to the transition are observed. We also study the equilibrium thermodynamics under ergodic conditions by heat capacity studies and determine the entropy-change and the adiabatic temperature change around the transition. We find agreement between the indirect and direct methods in determining the adiabatic temperature change and discuss the influence of nonergodic properties on the magnetocaloric effects.