In this paper, we intend to explain the behaviour of the evolved double-lined eclipsing binary TZ Fornacis on the basis of tidal evolution derived from standard theories and the use of modern internal structure stellar models. TZ For is a binary system with a period of 75.7days and a circular orbit, in which the less massive component (1.95Msun_) is rotating conspicuously faster than synchronism while its more massive mate (2.05Msun_) shows synchronized rotation with orbital motion. We discuss the use of the corresponding differential equations of tidal evolution, for the orbital eccentricity and the rotational velocities, instead of the generally assumed expressions for time scales. Results show that the integration of the differential equations provides a satisfactory explanation for the tidal and evolutionary status of TZ For. Using a normalized initial rotational velocity at the ZAMS for the components and assuming a rigid body rotation, we have found that at its present status, for an age of 1.3Gyears, the system should show a ratio between the individual rotational velocities of the two components, v_2_/v_1_, of around 11 in good agreement with the observed value.