P6 Settings That Change Your Dates
Last reviewed 16 September 20268 min read
Every setting that silently moves a date — one lookup table, with the page that argues each one
🟩 In one line: Twenty-two settings across Admin Preferences, Project Details, Scheduling Options, calendars and activity fields can change the dates P6 calculates without anyone editing a duration or a link; this page lists them, where they live, what they do, the hub's value for each, and the page that explains why.
👤 Who this is for: J/M/S. Prerequisite: none — this is the index. Companion to constraints-and-calendars (the 5-minute diagnostic).
First, let's be honest about why this page exists
"Nothing changed but the dates moved" is said at least once on every project. Something did change; it was a setting, and it was one of the twenty-two below. This page exists so the search takes five minutes instead of an afternoon.
Nothing here is argued. Every row points to the page that does the arguing.
🟨 The standard — what "good" looks like
| Source | What it asks for (paraphrased) | Consequence |
|---|---|---|
| AACE RP 38R-06 | Schedule basis records settings and assumptions | This table, with a screenshot, is SBM section 3 |
| DCMA 14-Point, Metrics 2, 3, 5, 9, 12 | Leads, lags, hard constraints, invalid dates, critical path test | Half the rows below are what those metrics detect |
| GAO Schedule Assessment Guide, BP 8 and 9 | Schedule reflects logic and calendars; updated correctly | Same |
| Convention (scheduling-options; hours-per-day-and-duration-display) | Settings table in SBM; screenshot in every transmittal; checked on every received file | The check is this table |
🟢 Rule: every row below is set at project set-up, screenshotted into the SBM, and re-checked on every received file before dates are read — and any date movement not explained by a duration, logic or progress entry is traced to one of these rows before anything else.
How it actually works
The table
| # | Setting | Where | What it does to dates | Hub value | Page |
|---|---|---|---|---|---|
| 1 | Use assigned calendar to specify the number of work hours for each time period | Admin → Admin Preferences → Time Periods | Off: durations display and convert at a fixed hours/day; a typed 10-day activity on a 10 h calendar shows as 12.5 | Ticked | hours-per-day-and-duration-display |
| 2 | Hours/day, days/week per calendar (Time Periods button) | Enterprise → Calendars → Modify → Time Periods | Sets how days convert to hours per calendar | 10 site; 24 curing; 8 office | hours-per-day-and-duration-display |
| 3 | Calendar work week and exceptions | Enterprise → Calendars → Modify | Non-work days and reduced hours push every finish | 6-day site; 7-day curing; Ramadan/summer as exceptions | calendar-setup-and-holidays |
| 4 | Calendar assigned to the activity | Activity Details → General | An activity on the wrong calendar finishes on the wrong day | Curing = 7-day; labour = 6-day | constraints-and-calendars |
| 5 | Global calendar edited | Enterprise → Calendars → Global | Every project using it moves | Never; project calendars | p6-global-vs-project-data |
| 6 | When scheduling progressed activities | Tools → Schedule → Options | Retained Logic / Progress Override / Actual Dates give different remaining-work dates on out-of-sequence activities | Retained Logic | retained-logic-vs-progress-override |
| 7 | Calculate start-to-start lag from | Schedule Options | Early Start vs Actual Start on progressed predecessors | Actual Start | scheduling-options |
| 8 | Calendar for scheduling relationship lag | Schedule Options | Predecessor / Successor / 24-hour / Project default — a 5-day lag can be 5 or 7 calendar days | Predecessor | calendar-on-relationship-lag |
| 9 | Define critical activities as | Schedule Options | Changes which activities are flagged critical — not their dates | Longest Path | critical-path-vs-longest-path |
| 10 | Compute Total Float as | Schedule Options | Start / Finish / Smallest — changes float shown, not dates | Finish Float | total-float |
| 11 | Calculate float based on finish date of | Schedule Options | Each project / opened projects — with several projects open, float measured to the latest of all | Each project | scheduling-options |
| 12 | Make open-ended activities critical | Schedule Options | Assigns late dates = early dates to dangles; changes float, not early dates | Unticked in submissions | open-ends |
| 13 | Use Expected Finish Dates | Schedule Options | On: an Expected Finish overrides remaining duration to hit the date | Ticked, and Expected Finish used only for site-given dates | forecasting-honestly |
| 14 | Level resources during scheduling | Schedule Options | Levelling delays activities to resource availability on every F9 | Unticked | resource-levelling |
| 15 | Schedule automatically when a change affects dates | Schedule Options | Reschedules on every edit; masks the effect of each change | Unticked | scheduling-options |
| 16 | Ignore relationships to and from other projects | Schedule Options | On: inter-project links no longer drive dates | Per SBM; usually unticked where links exist | interface-and-handover-logic |
| 17 | Data Date | Project Details → Dates / Schedule dialog | Every remaining activity is pushed to start no earlier than it | Same calendar day monthly; never moved between updates | data-date |
| 18 | Must Finish By | Project Details → Dates | A hidden project-level Finish On or Before; negative float appears with no visible constraint | Blank; constrained milestone instead | setting-up-a-p6-project |
| 19 | Planned Start | Project Details → Dates | Earliest start for the first activity when no predecessor | Contract commencement | setting-up-a-p6-project |
| 20 | Primary / secondary constraints on activities | Activity Details → Status | Hold, push or force dates against logic | Start On or After (access/deliveries) and Finish On or Before (contract milestones) only, each with a document reference | p6-constraint-types |
| 21 | Expected Finish on an activity | Activity Details → Status | Overrides remaining duration (when setting 13 is on); stays after completion unless cleared | Cleared on completion | forecasting-honestly |
| 22 | Duration Type | Activity Details → General / Project Defaults | Fixed Units/Time re-forecasts remaining duration from actual units; Fixed Units changes duration when crew edited | Fixed Duration & Units | p6-duration-types-explained |
| 23 | Percent Complete Type = Duration | Activity Details → General | Ties remaining duration to the percent; Update Progress moves both | Physical on production work | percent-complete-types |
| 24 | Activity Type = Resource Dependent | Activity Details → General | Activity follows resource calendars, not its own | Task Dependent unless deliberate | p6-activity-types-explained |
| 25 | Activity Type = LOE | Activity Details → General | Dates come from linked activities, not its own duration | LOE for scaffold, hoist, supervision only | p6-activity-types-explained |
| 26 | Resource calendar | Enterprise → Resources → Details | Drives Resource Dependent activities; ignored by Task Dependent | Per resource; recorded where used | resource-loading |
| 27 | Levelling priorities and options | Tools → Level Resources | Where levelling is run, decides which activity waits | Never on a contractual update | resource-levelling |
| 28 | Import configuration (calendars Update Existing) | File → Import → Configuration | Overwrites your calendars with the file's | Keep Existing; Prod-Safe | importing-and-exporting-xer |
| 29 | Update Baseline | Project → Maintain Baselines → Update | Changes baseline dates, not current ones — variance vanishes | Never on an accepted baseline | p6-baselines-assign-and-maintain |
| 30 | Merge Reflection (dates/durations ticked) | Right-click Reflection → Merge | Overwrites current actuals with the Reflection's older values | Tick only intended items; re-enter manually after source has moved | p6-reflections-and-what-if |
Rows 9, 10 and 12 change what is displayed as critical or as float, not the early dates — included because they are the commonest "the critical path changed" calls.
Settings that look like they change dates but don't
| Setting | Where | Effect |
|---|---|---|
| Durations shown in / Units per time | Edit → User Preferences → Time Units | Display only; a 10-day activity shown as 100 h is still 10 days — but two reviewers with different preferences will disagree about what they see |
| Date format, show time | Edit → User Preferences → Dates | Display; hiding the time is how a 17:00 finish and an 08:00 start on the same day look like a zero lag |
| Anticipated Start / Finish on WBS | WBS Details | Display on empty nodes; no effect once activities exist |
| Bar and timescale settings | Layout | Display |
The 5-minute order of search
Data date (17) → scheduling options screenshot vs current (6–16) → calendar assignment column grouped (4) → Admin hours tick (1) and calendar Time Periods (2) → constraint filter (20) and Expected Finish column (21) → Must Finish By (18) → duration and percent types grouped (22–23) → activity types (24–25) → scheduling log for loops and open ends. Then Schedule Comparison against the previous version to see which activities actually moved (p6-schedule-comparison).
🟥 Where people go wrong
- Editing durations to fix a settings problem. Hours per day off by two shows every duration wrong; correcting each activity destroys the basis. Fix the setting (rows 1–2); the durations were right.
- Reading dates on a received file before checking rows 6–16. Their Progress Override and Successor-calendar lag give a completion three weeks earlier than yours would from the same data. Screenshot comparison first.
- Forgetting Must Finish By. Negative float everywhere, no constraint visible in the activity table. Row 18, blank.
- Blaming logic for an Expected Finish. An activity refuses to move because an Expected Finish from four months ago is still on it. Column added, cleared.
- Two reviewers, two user preferences, one argument. Neither file changed; the display did. Rows in the second table; SBM screenshot settles it.
- No screenshot. The setting was changed in month 6 and nobody can prove what it was in month 1. SBM section 3, updated with every baseline revision.
⚖️ When you're challenged
"Nobody touched the programme and the completion moved 11 days." Somebody touched a setting. Working through the list: data date unchanged, scheduling options unchanged, calendar assignment — 26 curing activities added by the site team on the 6-day calendar instead of the 7-day. Reassigned, rescheduled, comparison shows the 11 days back. Change table has the line.
"Your file gives a different completion on my machine." Same file, so it's a setting on your side or a display preference. Admin Preferences hours tick and the scheduling options screenshot in the transmittal are the two to check first; if it's User Preferences, the dates are identical and only the duration column reads differently.
📄 Related pages
- Constraints and calendars — the 5-minute diagnostic this table expands
- Scheduling options — rows 6–16 in full
- Hours per day and duration display — rows 1–2
- Setting Up a P6 Project — where most rows are set
- P6 Schedule Comparison — proving which activities moved
- Cleaning an XER Before Import — the sandbox where this search happens on received files
- Schedule Basis Memorandum — where the screenshot lives
✏️ Worked example
Received subcontractor file, MEP package, Riyadh hospital: their PDF shows completion 14 March; imported into the sandbox it shows 2 April. Search in order:
| Row | Finding | Effect on completion |
|---|---|---|
| 17 | Data date matches | — |
| 6 | Their options: Progress Override; ours: Retained Logic | 9 days of the 19 |
| 8 | Their lag calendar: 24-hour; ours: Predecessor | 4 days |
| 1–2 | Their Admin tick off, 8 h fixed; their site calendar 10 h | Durations displayed 25% long in our DB, but stored hours identical — 0 days once row 1 ticked |
| 21 | 14 activities with Expected Finish dates from a prior update | 6 days |
| 20 | 3 Start On constraints with no reference | 0 days at completion (off-path), listed for the reconciliation table |
Nineteen days accounted for in 20 minutes. The reconciliation table went back with rows 6, 8 and 21 as questions, and the sub's next submission matched to within a day.
📖 References
- AACE International RP 38R-06, Documenting the Schedule Basis
- DCMA 14-Point Schedule Assessment, Metrics 2, 3, 5, 9, 12
- GAO Schedule Assessment Guide (GAO-16-89G), Best Practices 8, 9
- Oracle Primavera P6 Professional User Guide — Admin Preferences; Project Details; Schedule Options; Calendars; Activity Details; User Preferences; Import Configuration; Maintain Baselines; Reflections (field labels as in P6 Professional v20; earlier versions differ)
From the field
Notes, corrections and additions from people who've done this on a real job. Everything is checked before it appears here.
Loading notes…
Checked before it appears. No client, project or employer names. Your name is shown; your email never is. Terms.