Work Calendar (Calendar Setup)

A programme is only correct once the software knows which days your site does not work. The Work calendar setup window declares two things: the working days of the week and the list of holidays / days off. That configuration is shared by Gantt drawing (non-working days shaded grey), CPM working-day maths, Schedule Recovery, EVM, the Variance Dashboard and the lookaheads.

It is the five-minute step engineers skip, and then every finish date comes out a week early because Sundays and Tết were counted as working days.

Related commands

Command	What it does
Setup	Opens the schedule tool window that contains Calendar Setup
Auto Calc	Recalculates the schedule using the calendar you just declared
Auto Draw	Repaints the chart automatically once the new calendar is applied
Gantt Chart	Redraws the chart so the shaded days and new finish dates show up
Update Status	Scores PV / SV / SPI on top of a correct calendar

Declaring the calendar for a project

1. Open a workbook with a schedule sheet, then go to DVD Cons → Schedule → Setup. The window opens on the Gantt Setup tab; choose Calendar Setup.
2. 🗓 WORK WEEK section — tick the working days (Mon … Sun). Unticked days are shaded grey on the Gantt and skipped when counting Working Days. Two Quick presets are provided: Mon → Fri (Office — 5 days) and Mon → Sat (VN site — 6 days).
3. 🎉 HOLIDAYS / DAYS OFF section — add holidays two ways:
   • VN preset: pick a year in the drop-down and click Apply VN holidays. The add-in reports how many dates were added and how many were skipped as duplicates.
   • By hand: pick a date in Add date, type a name in the Holiday name (e.g. Company anniversary) box, then click + Add. A duplicate date is rejected with "Date … is already in the list."
4. Review the holiday grid with its ✓ / Date / Day / Holiday name / Delete columns. Untick ✓ to disable a date without removing it; click ✕ to delete it.
5. Check the statistics strip below: Working days / week, Holidays (Enabled) and Working days in …; click ⟳ Recalculate after edits to refresh the numbers.
6. Click Save. At least one working day per week is required, otherwise the window reports "There must be at least one working day in the week."
7. Back on the schedule sheet, click Gantt Chart (or turn on Auto Draw and edit a cell) so the chart and the finish dates pick up the new calendar.

Example

A site works Mon–Sat, rests on Sunday, year 2026. Click Mon → Sat (VN site — 6 days), choose 2026 and click Apply VN holidays — the list receives the official public holidays. The preset writes the Vietnamese names, whatever UI language you use:

Date	Holiday name as inserted	Meaning
01/01/2026	Tết Dương lịch	New Year's Day
17/02 → 21/02/2026	Tết Nguyên Đán (mùng 1 … mùng 5)	Lunar New Year, days 1–5
26/04/2026	Giỗ Tổ Hùng Vương	Hung Kings' Commemoration Day
30/04/2026	Giải phóng miền Nam	Reunification Day
01/05/2026	Quốc tế Lao động	International Labour Day
02/09/2026	Quốc khánh	National Day

The activity Internal plaster, level 2 starts on 27/04 with a duration of 6 days. Before the calendar was declared the add-in returned a finish of 02/05; afterwards 30/04 and 01/05 are excluded and the finish moves to 05/05 — which is what actually happens on site.

Tips and caveats

• The VN preset only carries lunar-calendar data for 2025–2030 (Lunar New Year and Hung Kings' Day are pre-loaded). Pick a year outside that range and the preset adds only the fixed Gregorian holidays — you add the lunar ones by hand.
• The preset covers days 1 to 5 of Tết; in years when the government grants a longer break (New Year's Eve, day 6), add those dates manually.
• The preset does not add substitute days off when a holiday falls on a weekend — check the annual government notice.
• On Save, the configuration is stored for your Windows user account and synced into the workbook through two named ranges, LichLamViec and DSNgayLe (created on a very hidden _DVDConfig sheet if the workbook has none). Do not edit that sheet by hand.
• Because the calendar is per user, the same file opened on another machine can produce different dates if that machine declares a different calendar — agree one calendar across the team before sharing files.
• ↺ Reset to defaults returns the week to Mon–Sat and clears every holiday; the reset only takes effect once you click Save.
• Editing the calendar does not repaint an existing chart and does not recalculate the sheet on its own — click Gantt Chart or run Auto Calc once.
• Do not confuse this with Pick Rest Days in the QAQC and Diary group: that command fills a string of non-working dates into a cell of the diary table and has nothing to do with schedule calculation.

See also

• Gantt Chart — building and drawing the schedule on top of this calendar.
• Advanced Scheduling — EVM, Variance Dashboard and the lookaheads all share this calendar.
• Setup — the window's other two sections: General Settings and Column Visibility.
• Auto Calc — how the working-day recalculation cycle behaves.