HKSM
Earned Schedule (ES)
A time-based extension of Earned Value Management that assesses schedule performance in units of time rather than cost.
Key Points
- ES translates the earned value (EV) into the point in time on the planned value curve where that EV would have been planned.
- Core indicators: SV(t) = ES - AT (schedule variance in time) and SPI(t) = ES / AT (schedule performance index in time), where AT is the actual time elapsed to the status date.
- Unlike traditional SPI and SV, ES-based metrics continue to show meaningful schedule performance near project completion.
- Helps forecast finish dates, assess schedule buffers, and integrate time-focused insights with standard EVM cost metrics.
Example
A project is at week 20 (AT = 20). The earned value achieved to date equals the planned value that was scheduled for week 18. Therefore, ES = 18 weeks. SV(t) = 18 - 20 = -2 weeks (behind schedule), and SPI(t) = 18 / 20 = 0.90.
PMP Example Question
At the status date, AT = 24 weeks and ES = 21 weeks. What is the best interpretation of these results?
- The project is 3 weeks under budget.
- The project is 3 weeks ahead of schedule.
- The project is 3 weeks behind schedule based on time-focused EVM.
- The project is performing as planned because SPI is 1.0.
Correct Answer: C — Earned Schedule indicates the work accomplished corresponds to week 21 while 24 weeks have elapsed.
Explanation: SV(t) = ES - AT = 21 - 24 = -3 weeks, showing the project is 3 weeks behind schedule using the Earned Schedule method.
