In construction projects, due to different reasons, the duration time for accomplishing specific project activities is subject to change. If these changes are not considered during the scheduling phase, the activities will be confused. Such confusion causes unexpected resource allocation and unexpected completion time of the project. Therefore, it is necessary to carry out an estimation study. This paper has two-fold objectives. First is to review thoroughly the uncertain problem in this field, and second is to propose an algorithm based on a statically calculation of all possible cases of changes. It is found that despite the success of the traditional methods in scheduling some of the presented examples; it seems to be fooled by the variable distribution of uncertainty across different projects, eventually leading to its failure. It was also found that uncertainty impacts construction projects to different degrees. The results of the proposed algorithm contribute to further analysis of the uncertain problem.