Work with the example
How many office days are in this supplied interval? The fictional calendar excludes Saturday/Sunday and has two closure slots D5:D6. Start and end are included when they are valid weekdays. It is not a Hong Kong public-holiday or payroll calendar.
| Input | Date |
|---|---|
| Start B5 | 2026-10-12 |
| End B6 | 2026-10-19 |
| Closure D5 | 2026-10-14 |
| Second slot D6 | True blank |
Edit the working cells
F5 guards numeric endpoints, reversed dates, and closures that must be numeric or truly blank, then uses NETWORKDAYS(B5;B6;D5:D6). Baseline 5 counts October 12,13,15,16,19. Add October 16 in D6:4. Fresh start=end October 12 with only October 14 closure gives 1; mark October 12 closed and it gives 0. Text in a closure slot gives Check closures.
Check the failure case
B6-B5 gives 7 calendar-day difference, not 5 office days. A date-looking text closure must not silently be ignored as if the calendar were complete.
If a single weekday interval is itself closed, how many office days remain?
Show the worked answer
Zero; the included endpoint is removed by the supplied closure.