The well-known event sequence chart in FIDIC 1999 and 2017 forms includes the Base Date, which is defined as 28 days before the final tender submission date.
This same definition appears in Sub-Clause 1.1.3.1 (FIDIC 1999) and Sub-Clause 1.1.4 (FIDIC 2017). However, the role of the Base Date is often reduced or bypassed in actual contracts due to modifications introduced through the Particular Conditions.
Why Is the Base Date So Important During Construction?
The Base Date serves a clear purpose in FIDIC:
It establishes a fixed reference point in time from which contractual progress and external impacts are evaluated fairly. Events such as:
- Unforeseeable physical conditions
- Availability of site data
- Changes in legislation
- Changes in cost
…are typically assessed by referring back to the Base Date.
Why Isn’t the Base Date Widely Used?
Among these events, the most directly linked to the Base Date is the Changes in Cost clause (Sub-Clause 13.8 in FIDIC 1999 and Sub-Clause 13.7 in FIDIC 2017). It allows either party to claim cost adjustments based on changes after the Base Date.
However, since prices tend to rise, many Employers and Developers disable this clause through Particular Conditions. Their goal is to avoid upward price adjustments, making the clause less useful in practice. As a result, the importance of maintaining the Base Date in its original FIDIC format often fades.
To retain some utility, contracts sometimes replace the standard Base Date with:
- A specific calendar date
- The actual tender submission date
- The Letter of Acceptance (LOA) date
This approach weakens its original intent but simplifies cost control.
Base Date—Present but Powerless?
Although the Base Date is structurally embedded in both FIDIC 1999 and 2017, its practical influence depends on how the Particular Conditions are drafted. In many cases, its most impactful use—cost variation claims—gets deactivated, leaving it as a placeholder with limited value.
Still, understanding its intended purpose helps stakeholders appreciate how contractual balance can be affected when this mechanism is altered or ignored.