Curtains, gates and freeze windows — mark the dates that matter

Some of the most important dates on a programme aren't bars at all. They're windows — the fortnight you have to mobilise, the change-freeze before go-live, the shutdown slot you cannot overrun. On a bar chart, those windows are invisible. A shaded vertical curtain fixes that in one stroke: it drops a coloured band across the whole timeline so nobody in the room can miss the date range that governs everything else.

Think about the last time a schedule review went sideways over a date everyone had "known about." The mobilisation window that closed while the paperwork was still moving. The code freeze someone shipped through anyway. The turnaround slot that quietly slipped a week and took the whole outage plan with it. In each case the date wasn't hidden — it was just one milestone diamond in a forest of bars, and the eye slid straight past it.

Bars answer how long. Milestones answer when. But neither shouts this range of dates is special — plan around it. That's the job of a curtain: a shaded band spanning a date range, drawn behind the bars, so the constraint reads before anyone even looks at an activity.

What a curtain is for

A curtain is a vertical band tied to a date or a date range, sitting behind the Gantt. It doesn't consume resources, it isn't on the logic — it's a presentation device that marks a region of time as meaningful. A few windows earn one on almost every programme:

• Gates and stage boundaries. A narrow band on the gate date — RIBA stage change, phase gate, investment decision — with the milestone diamond sitting right on it. The band says "everything to the left had to be done by here."
• Mobilisation windows. The slot in which site set-up, access or possession must happen. Miss the near edge and the far edge starts eating your float.
• Freeze and blackout windows. Change freezes before a go-live, financial period-end blackouts, peak-trading no-deploy windows. Nothing should land inside the band.
• Outage, shutdown and turnaround windows. The fixed slot when the plant is down and the clock is merciless — every work-front has to fit inside the band, and overrun costs real money per hour.
• Phase boundaries. Alternating faint bands per phase turn a long timeline into readable chapters without a single extra row.

Drawing one, in four moves

The workflow is the same whatever the window is. Once you've done it once, a curtain takes about fifteen seconds.

1. Pick the date range. Decide the two edges — a single date for a gate (the band becomes a thin marker), or a start and finish for a window. Use real dates from the schedule: the go-live date for a freeze, the possession dates for a mobilisation, the outage slot for a shutdown.
2. Add a curtain. Drop a curtain on the timeline and set its start and finish. It draws as a shaded band behind the bars, spanning the full height of the chart, on the same axis as everything else — so it lines up with the dates automatically.
3. Label and colour it. Give it a title ("Change freeze", "Outage — Unit 2") and a fill colour that carries meaning: red for a hard do-not-cross, amber for caution, teal for a planning window. Keep the fill faint so bars stay readable through it.
4. Layer milestones on top. Drop the governing milestone onto the band edge — the go-live diamond on the freeze's closing edge, the gate diamond on the gate band. Now the window and its trigger read as one object.

Three windows, three contexts

Construction — the mobilisation window

You have possession of the site from a fixed date, and enabling works must be complete before main construction can start. Draw a teal mobilisation band across those weeks. Instantly the site-set-up, welfare, hoarding and temporary-works bars have a visible box to live inside — and if any of them pokes out the right-hand edge, the slip is obvious to a director who has never read a Gantt in their life.

Software — the change-freeze before go-live

Two weeks before a release, changes stop. Draw a red freeze band from freeze-start to go-live, and put the go-live diamond on its closing edge. Any development bar that overlaps the band is a conversation you want to have now, in the review, not on the morning of the release. The band makes the rule visual: nothing merges inside the red.

Operations — the shutdown / turnaround window

The plant is down for a fixed outage and every hour is costed. Draw an amber shutdown band across the slot; every mechanical, inspection and re-instatement work-front has to fit inside it. Overlay the data-date line and you can see, mid-outage, whether the work fronts are tracking to close before the window does — the single most important question in the room.

Curtains plus a data-date line: the story reads itself

A curtain on its own marks a window. Pair it with the data-date line and it starts telling a live story. Where the dashed "now" line sits relative to the band answers the question everyone's actually asking:

• Data date left of the band — the window is ahead of you. Are the activities that must finish before it on track to clear?
• Data date inside the band — you're in it. For a shutdown, that's the pressure cooker; is the work closing faster than the window?
• Data date right of the band — the window's behind you. Did everything that had to happen inside it, happen?

Add the governing milestone on the band edge and you've got three primitives — window, trigger, now — composing a complete picture with no words. A director reads it in the two seconds before you've finished saying "next slide."

Why this is a first-class device, not a workaround

Here's the thing planners run into. The desktop scheduling tools that own the network logic have no clean way to present a freeze or an outage window. You end up drawing a coloured rectangle by hand in a slide, floating it over a pasted screenshot, and then re-aligning it every single month when the dates move and the screenshot changes size. The band and the schedule live in two different tools, and they drift apart the moment anything updates.

A curtain that's part of the schedule doesn't drift. It's anchored to real dates on the same axis as the bars, so when the timeline re-scales for print or export, the band moves with it and stays exactly where the dates say it should. Label it once, colour it once, and it's correct on every export — PDF, PowerPoint, PNG, a read-only link — forever. That's the difference between a decoration you maintain by hand and a presentation primitive the tool draws for you.

Primavera and P6 are trademarks of Oracle Corporation; Microsoft Project is a trademark of Microsoft Corporation. Sketchedule is an independent product and is not affiliated with, endorsed by or sponsored by Oracle or Microsoft. Figures are illustrative, drawn in Sketchedule.