The ``contract,'' ``custom'' or ``practice'' on which the
compensability of the activities referred to in section 4 of the Portal
Act may be based, is a contract, custom or practice in effect ``at the
time of such activity.'' Thus, the compensability of such an activity,
and its inclusion in computation of hours worked, is not determinable by
a custom or practice which had been terminated before the activity was
engaged in or was adopted some time after the activity was performed.
This phrase would also seem to permit recognition of changes in customs,
practices and agreements which reflect changes in labor-management
relations or policies.
