Calculating Start and Finish Dates
Part of creating a precedence diagram is calculating the start and end dates for each activity. Two processes that help you do this are the forward pass and the backward pass.
Applying the Forward Pass
The forward pass is used to calculate the ES and EF dates of all network activities. Here are the steps to follow.
The first activity starts on day 1 of the project; therefore that is the ES date for that activity. In the following example, the first activity is Mix Concrete. Its ES is day 1, the first day of the project.
Now you can calculate the EF for the first activity by adding the activity's duration to the ES. In this case, the duration is 6 days, so the EF is 7.
The ES for the next activity is the EF of the preceding activity. In our example, the ES for Pour Concrete is the EF for Mix Concrete, 7. Add this to the duration of the second activity, 4, to get its EF, 11.
By going through the entire diagram in this way, you will arrive at the project's EF, the earliest date the project can finish.
The formula for the forward pass is ES + duration = EF.
One point to keep in mind is that some activities have multiple predecessors. The ES is the earliest date that all the dependencies have been satisfied.