SCHEDULING

Time & Day Calculations in Excel

Beyond charting a Gantt-style schedule, most project timelines come down to simple date math: how many days until this is due, what date do we finish if we start Monday, and how many hours did the crew actually work. Excel has purpose-built functions for all three that most people don't know exist.

1
Calculate days between two dates.
With a start date in A2 and end date in B2, =B2-A2 gives the number of days between them. Format the result cell as Number (not Date) — Excel defaults to showing it as a date otherwise, which looks wrong even though the math is correct.
2
Count only working days (skip weekends).
=NETWORKDAYS(A2,B2) counts weekdays only between two dates, automatically excluding Saturdays and Sundays — useful for estimating actual crew-days on a job rather than raw calendar days.
3
Exclude holidays too.
List your holiday dates in a range (say H2:H10), then use =NETWORKDAYS(A2,B2,H2:H10) — the third argument excludes those dates from the working-day count as well.
4
Find a completion date from a start date + duration.
=WORKDAY(A2,15,H2:H10) answers "if we start on this date and the job takes 15 working days, what date do we finish?" — again skipping weekends and any holiday list you provide.
5
Track labor hours from clock-in/clock-out times.
With a start time in C2 and end time in D2, =D2-C2 gives elapsed time. Format the cell as [h]:mm (not the standard time format) so shifts longer than 24 hours in a weekly total still display correctly instead of resetting to zero.
For a live "days remaining" countdown that updates every time the sheet is opened, use =DeadlineCell-TODAY(). Since TODAY() recalculates automatically, you never have to manually update it — just don't use it in a sheet you need frozen for historical record-keeping, since older printouts will show a different countdown than the live file.

Combined, these five formulas cover the vast majority of date math a project actually needs — from bid deadlines to crew scheduling to payroll hours — without needing a separate scheduling tool for the calculation itself.

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