During treatment of a delayed schedule,specific deliberation of calculation on claim for extension of time should be paid attention to the following tasks:because the critical path of a network might be changed from time to time and the appropriate utilization of float should be carefully considered in the actual schedule,therefore,the claim for extension of time can not be calculated only by the network,but the actual period where the cause of a delayed schedule is set should be considered,and should be calculated on the basis of the actual schedule which is approved by the supervising Engineer.