My Partial Holiday Reduced Too Much or Too Little Capacity

A partial-day holiday reduces capacity by the overlap between its window and the shift, and it subtracts that time before multiplying by instances and utilization, so the machine-hours removed are usually larger than the clock hours of the closure. A cut that looks too big is the per-instance multiplication; a cut that looks too small is usually no overlap.

EDGEBIC by User Solutions treats a partial holiday the way it treats scheduled downtime: it trims the overlapping hours from a shift, then applies the instance count and utilization to what remains. This post covers a partial holiday that reduced too much or too little; it sits in the EDGEBIC troubleshooting guide and pairs with how to add a plant holiday and how EDGEBIC calculates work center capacity.

First, Know the Order of the Math

For one shift on one day, the engine takes the gross shift hours, subtracts the break, the downtime, and the partial-holiday overlap to get net hours, then multiplies net by the number of instances and by the utilization percentage. The partial-holiday hours are the overlap between the holiday window and the shift window: the later of the two start times to the earlier of the two end times, floored at zero. Two facts fall out of this. The cut is per instance, so it multiplies up. And the cut is only the overlap, so a window outside the shift removes nothing.

Cause 1: The Cut Multiplied by Instances (Looks Too Big)

A two-hour partial holiday on a work center with three instances removes two hours from each instance's day. Before utilization scaling, that is about six machine-hours, not two. Planners who expect a flat reduction across the whole work center read this as too much.

How to tell: the reduction is roughly the closure hours times the instance count (then scaled by utilization). Open the per-day capacity for the work center and date, and the remaining hours reconcile with net hours, minus the overlap, times instances, times utilization. If the number still looks off after that arithmetic, check for scheduled downtime on the same day, which is subtracted at the same point in the calculation and stacks with the partial-holiday overlap before the multipliers apply.

Fix: none; this is correct and matches downtime. If the intent was to remove only one machine's time, model that as downtime on a single instance rather than a plant-wide partial holiday, which applies to every instance.

Cause 2: The Window Does Not Overlap the Shift (Looks Too Small)

Capacity is cut only where the holiday and the shift intersect. A holiday set for early morning on a work center whose day shift starts later has zero overlap and removes nothing.

How to tell: the holiday's start and end times sit partly or wholly outside the shift's daily hours, so the overlap is small or zero.

Fix: set the holiday window to cover the shift hours you actually want closed. If you meant the whole day, use the whole-day setting instead of a partial window, which blocks the shift entirely rather than trimming an overlap.

Cause 3: The Whole-Day Flag Is Wrong

The whole-day setting and the partial window are mutually exclusive. A closure marked whole-day blocks the entire day; one marked partial trims only the window. Setting the wrong one is a common over- or under-cut.

How to tell: you intended a partial trim but the day is fully blocked, or you intended a full closure but only a slice was removed.

Fix: set the whole-day flag to match intent. Whole-day for a full closure; partial with a start and end time for a trim.

Cause 4: A Per-Day Override Is Masking It

If a per-day capacity override exists for that work center and date, the engine uses the override hours as the effective capacity as-is and does not re-apply the partial holiday on top. An override can therefore hide a closure.

How to tell: the per-day capacity for the cell shows an override value, and the holiday appears to have no effect.

Fix: remove the override so the calendar math applies, or fold the closure into the override value directly if you want to keep the override.

The Reconciliation, in Order

1. Compute the overlap between the holiday window and the shift window.
2. Remember the overlap is subtracted per instance, then scaled by utilization.
3. Check the whole-day flag matches whether you meant a full closure or a trim.
4. Confirm the window actually intersects the shift; no overlap means no reduction.
5. Look for a per-day override on the cell that overrides the calendar math.

Prevention

• Set the partial window to overlap the shift you mean to close, since only the intersection counts.
• Expect per-instance scaling. A partial closure on a multi-machine work center removes far more than its clock hours.
• Use whole-day for full closures rather than a window that spans the shift, which is clearer and less error prone.
• Watch for per-day overrides, which set effective hours directly and bypass the holiday math.
• Reconcile against the per-day capacity view, which shows the remaining hours for the exact work center and date, so you can check the arithmetic rather than guessing at the reduction.

If the holiday removed no capacity at all, that broader case is covered in a holiday did not reduce capacity, and a job that landed on a closed day is covered in job scheduled on a holiday.