Date constraint: the delay in front of the date stopped travelling

One activity carries a fixed start date and its predecessor runs 26 days late. Under the fixed date none of the delay reaches completion, and read as not earlier than, 17 days walk through.

Live result

Under a fixed start, 26 delay days stop at the successor and completion moves 0 days.

actual predecessor finish2026-02-06
overlap the sequence does not support17 days

A fixed start holds the date by pushing the delay into an overlap nobody typed.

Try a record

Actual predecessor finish2026-02-06date

This is the one date moved by the chart and the exact daily sweep.

Tracked date reading

Edit the chain and sweep dates

Predecessor

Activity name

Planned predecessor start

Durationdays

Successor

Activity name

Durationdays

Actual predecessor finish

Successor constraint date

Typed completion target

Relationship: Finish to start

Exact daily sweep

First actual finish date

Last actual finish date

Tracked reading: Fixed start
Delay stops at: Frame
First tracked change below: 2026-02-05
First tracked change above: 2026-02-07

Two date readings and the exact daily sweep

fixed start

Successor start: 2026-01-20
Completion: 2026-01-25
Completion movement: 0 days
Delay stopped: 26 days
Delay reaching completion: 0 days
Unsupported overlap: 17 days
Predecessor total float: −17 days
Successor total float: 16 days

not earlier than

Successor start: 2026-02-06
Completion: 2026-02-11
Completion movement: 17 days
Delay stopped: 9 days
Delay reaching completion: 17 days
Unsupported overlap: 0 days
Predecessor total float: −1 day
Successor total float: −1 day

Both date readings
Measure	Fixed start	Not earlier than
Successor start	2026-01-20	2026-02-06
Completion	2026-01-25	2026-02-11
Completion movement	0 days	17 days
Delay stopped	26 days	9 days
Delay reaching completion	0 days	17 days
Unsupported overlap	17 days	0 days
Predecessor total float	−17 days	−1 day
Successor total float	16 days	−1 day

This reads the dates, durations, target, and finish to start relationship typed by the visitor. It does not decide whether a date constraint is proper, whether an overlap could be worked, who carries delay, whether time or money follows, or what any schedule specification requires.

Here is the maths

The formula, in words

Treat every date as an exclusive civil day boundary. Planned predecessor finish is planned start plus predecessor duration. Fixed start always places the successor on the constraint date. Not earlier than places it on the later of the constraint date and predecessor finish. Successor completion is its resulting start plus its duration.

F_p=S_p+d_p

where

F_p

is planned predecessor finish,

S_p

planned predecessor start, and

d_p

predecessor duration.

S_f=C,\qquad S_n=\max(C,F_a)

\begin{gathered}S_f=C, \\ S_n=\max(C,F_a)\end{gathered}

where

S_f

is the fixed successor start,

C

the constraint date,

S_n

the not earlier than successor start, and

F_a

actual predecessor finish.

E_f=S_f+d_s,\qquad E_n=S_n+d_s

\begin{gathered}E_f=S_f+d_s, \\ E_n=S_n+d_s\end{gathered}

where

E_f

is fixed completion,

d_s

successor duration, and

E_n

not earlier than completion.

A worked example

Foundation starts on 2026-01-01 and lasts 10 whole days, so its planned finish boundary is 2026-01-11.

Its actual finish on 2026-02-06 is 26 days late. The Frame constraint date is 2026-01-20, leaving an original gap of 9 days.

With fixed start, Frame still runs from 2026-01-20 to 2026-01-25. All 26 delay days stop, zero reach completion, and 17 days overlap without support from the typed sequence.

With not earlier than, 9 days are absorbed and 17 reach completion. Frame runs from 2026-02-06 to 2026-02-11, which is 1 day beyond the typed target.

How the two float readings are formed

Under fixed start, predecessor total float is the constraint date minus predecessor finish, while successor total float is the typed target minus model completion. Under not earlier than, both use the target derived late successor start. A negative number names an overlap against the relationship date or a miss against the typed target, as stated beside it. It does not assign fault.

\phi_{p,f}=C-F_a,\qquad \phi_{s,f}=T-E_f

\begin{gathered}\phi_{p,f}=C-F_a, \\ \phi_{s,f}=T-E_f\end{gathered}

where

\phi_{p,f}

is predecessor float under fixed start,

\phi_{s,f}

successor float under fixed start, and

T

the typed target.

L=T-d_s,\qquad \phi_{p,n}=L-F_a,\qquad \phi_{s,n}=L-S_n

\begin{gathered}L=T-d_s, \\ \phi_{p,n}=L-F_a, \\ \phi_{s,n}=L-S_n\end{gathered}

where

L

is the late successor start,

\phi_{p,n}

predecessor float under not earlier than, and

\phi_{s,n}

successor float under not earlier than.

What this does not model

It does not decide whether the date constraint is proper, whether the apparent overlap can be worked, who carries delay, whether time or money follows, or what a schedule specification requires.

What the sweep moves

Only actual predecessor finish moves. Every civil date in the typed inclusive range is evaluated without sampling. Activity names, durations, relationship, constraint date, target and selected reading hold fixed.

Permanent refusal

Responsibility, entitlement, compensability, overlap feasibility and schedule compliance are outside the exact input contract. A field asking for any of them is refused rather than ignored.

The calculation domain

The chain contains one finish to start relationship, durations from 1 to 366 whole days, possible Gregorian dates in YYYY MM DD form, and an inclusive sweep spanning no more than 366 days.

Boundary

Source anchors

Oracle Primavera Cloud documentation, activity constraints and relationship logic.
Society of Construction Law, Delay and Disruption Protocol, second edition, 2017.

The sources are cited for the distinction between calculated sequence logic and imposed dates. No source definition, table or method is reproduced. The civil date arithmetic is stated independently on this page.

Calculation version

1.0.0

The whole record prints. Your browser can save it as a PDF instead of printing it.

Oracle scheduling documentation and the Society of Construction Law Delay and Disruption Protocol are cited by structure and not reproduced. Responsibility, entitlement, compensability, overlap feasibility and schedule compliance are permanently outside this page. Its two readings describe only the typed chain and do not determine whether either setting is proper for a real programme.

Fixed date chain record

Date constraint: the delay in front of the date stopped travelling

Accepted inputs

Predecessor, Activity name: Foundation
Planned predecessor start: 2026-01-01
Predecessor, Duration: 10 days
Successor, Activity name: Frame
Successor, Duration: 5 days
Actual predecessor finish: 2026-02-06
Relationship: Finish to start
Successor constraint date: 2026-01-20
Typed completion target: 2026-02-10
Tracked date reading: Fixed start
First actual finish date: 2026-01-05
Last actual finish date: 2026-02-10

All results

fixed start, Successor start: 2026-01-20
fixed start, Completion: 2026-01-25
fixed start, Completion movement: 0 days
fixed start, Delay not reaching completion: 26 days
fixed start, Delay reaching completion: 0 days
fixed start, Unsupported overlap: 17 days
fixed start, Predecessor total float: −17 days
fixed start, Successor total float: 16 days
not earlier than, Successor start: 2026-02-06
not earlier than, Completion: 2026-02-11
not earlier than, Completion movement: 17 days
not earlier than, Delay not reaching completion: 9 days
not earlier than, Delay reaching completion: 17 days
not earlier than, Unsupported overlap: 0 days
not earlier than, Predecessor total float: −1 day
not earlier than, Successor total float: −1 day
First tracked change below: 2026-02-05
First tracked change above: 2026-02-07

Record fields

Calculation version: 1.0.0
Boundary: This reads the dates, durations, target, and finish to start relationship typed by the visitor. It does not decide whether a date constraint is proper, whether an overlap could be worked, who carries delay, whether time or money follows, or what any schedule specification requires.
Calculation trace: Treat every date as an exclusive civil day boundary. Planned predecessor finish is planned start plus predecessor duration. Fixed start always places the successor on the constraint date. Not earlier than places it on the later of the constraint date and predecessor finish. Successor completion is its resulting start plus its duration.
$F_p=S_p+d_p$
where $F_p$ is planned predecessor finish, $S_p$ planned predecessor start, and $d_p$ predecessor duration.
$S_f=C,\qquad S_n=\max(C,F_a)$ $\begin{gathered}S_f=C, \\ S_n=\max(C,F_a)\end{gathered}$
where $S_f$ is the fixed successor start, $C$ the constraint date, $S_n$ the not earlier than successor start, and $F_a$ actual predecessor finish.
$E_f=S_f+d_s,\qquad E_n=S_n+d_s$ $\begin{gathered}E_f=S_f+d_s, \\ E_n=S_n+d_s\end{gathered}$
where $E_f$ is fixed completion, $d_s$ successor duration, and $E_n$ not earlier than completion. Only actual predecessor finish moves. Every civil date in the typed inclusive range is evaluated without sampling. Activity names, durations, relationship, constraint date, target and selected reading hold fixed.
Source anchors: Oracle Primavera Cloud documentation, activity constraints and relationship logic. Society of Construction Law, Delay and Disruption Protocol, second edition, 2017.

Two date readings and the exact daily sweep

fixed start

not earlier than

Here is the maths

The formula, in words

A worked example

How the two float readings are formed

What this does not model

What the sweep moves

Permanent refusal

The calculation domain

Boundary

Source anchors

Calculation version

Related

Accepted inputs

All results

Record fields