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Early Start Date

Early Start Date (ES)

Scheduling Terms Reviewed by forProject Technology - updated Sep 2026
Quick definition: The Early Start Date is the earliest a task can begin, given its predecessor relationships — including their type and any lead or lag — and its working calendar.

Calculated during the Forward Pass, the Early Start Date is the soonest a task could begin once every predecessor relationship is satisfied. What that requires depends on the relationship type: a Finish-to-Start predecessor must finish first, while a Start-to-Start predecessor need only start. Any lead or lag shifts the result further, and the task's working calendar determines the actual date, since non-working days are skipped. It works alongside the Early Finish Date to establish the earliest possible schedule for each task.

Why it matters

The Early Start Date, compared against the Late Start Date, shows how much flexibility a task has before it must begin — a key input for calculating float and identifying the Critical Path. It's foundational to how scheduling software calculates the overall schedule.

Also known as
N/A
Used in
Critical Path Method (CPM) Forward Pass calculations; Total Float and Free Float calculations

FAQ

How is Early Start Date different from Late Start Date?
Early Start Date is the soonest a task could begin; Late Start Date is the latest it can begin without delaying the project — the difference between them is the task's float.
Is the Early Start Date always the date a task should actually start?
Not necessarily — it's the earliest theoretical start, but resource availability or other constraints may mean the task is planned to start later.
Definition maintained by forProject Technology.
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