Working Day vs Calendar Day in Production Scheduling

Working days count only the dates the plant actually operates, while calendar days count every date including weekends and holidays. The distinction matters for any scheduling delay measured in days, because a weekend or a closure falling inside the window changes where the next step lands. Three working days and three calendar days start at the same point but often finish on different dates. EDGEBIC by User Solutions lets you count a between-step delay either way, so the timeline reflects how the real-world delay actually behaves.

How it works

Several scheduling delays are expressed in days rather than hours. The most common is transit time, the days it takes parts to travel between two routing steps, such as sending work out to a vendor for heat treatment or anodizing. When you set a days-based delay, you also choose whether it counts calendar days or working days.

Calendar days count straight through the week. If a step finishes Thursday and the delay is three calendar days, the clock ticks Friday, Saturday, Sunday, and the next step becomes eligible on Sunday. Working days skip the days the plant is closed. The same three working days starting Thursday tick Friday, then skip the weekend, then Monday and Tuesday, landing the next step on Tuesday.

Neither mode adds or removes capacity. It only decides where the successor step becomes eligible to start. The engine still places that step on real available hours, so a delay that lands on a closed date is pushed forward to the next open slot regardless.

A concrete example

Think of the difference the way you would judge a delivery promise. A courier that quotes three-day shipping means three calendar days: the package moves over the weekend whether or not your office is open, so a Thursday shipment arrives Sunday. The delay does not care about your hours. That is calendar days.

Now think of an internal task that only advances when your team is at work, such as a document that has to sit two business days for review. Those two days skip the weekend, because the review only happens on working days. Ship it Friday and it is ready Tuesday, not Sunday. That is working days.

In the plant, parts sent to an outside anodizing vendor for three working days come back on the third day the vendor and your receiving dock both run, while a shipment quoted in calendar days advances even across your weekend. Matching the count to the real behavior is the whole point: an outbound freight tail is usually calendar days, an internal queue is usually working days.

How EDGEBIC uses it

The working day versus calendar day choice appears wherever a delay is measured in days. Transit time between routing steps is the clearest case, and it is explained inside EDGEBIC queue and transit times. The related concept of the whole gap a shipment introduces is covered in what is transit time in production scheduling.

Because the mode only shifts where a step lands, it works alongside the capacity calendar rather than replacing it. A transit delay counted in working days still respects plant holidays, so the parts do not "arrive" on a closed date and the next operation still waits for real hours. The end-item delivery tail, the cure or ship time after the last operation, uses calendar days for the same reason a courier does: the clock runs whether or not the plant is open.

Getting the count right stops two quiet errors: hidden slack when you use working days for a delay that ignores your hours, and impossible arrivals when you use calendar days for a delay that only advances at work. For the wider vocabulary, see the manufacturing glossary, and to see days-based delays inside a working plan, explore EDGEBIC.