Date and Work Time Calculator

Choose a mode and calculate

1. Select a mode tab.
2. Complete its required labeled fields and any relevant shared settings.
3. Select Calculate business days, Calculate resulting date, Calculate elapsed duration, Calculate week number, Calculate countdown, or Calculate timesheet.
4. Read the result. If validation fails, the tool displays a specific error message instead.

What each mode calculates

• Business Days counts dates inclusively using the selected weekdays and dates entered in Holidays to exclude.
• Add / Subtract adds or subtracts calendar days, business days, weeks, months, or years from a Base date.
• Elapsed Duration compares two date-times in the selected Time zone and reports the duration.
• Week Number returns the ISO week, ISO week-numbering year, and that week's Monday-to-Sunday dates.
• Countdown compares a target date-time with your device's current instant.
• Work Hours & Timesheet calculates gross, break, paid, regular, and overtime hours by shift, date, and ISO week.

Set the shared options that affect your result

• Locale (display formatting) changes displayed dates, times, and numbers.
• Time zone applies to date-times in Elapsed Duration, Countdown, and Work Hours & Timesheet.
• The Weekday schedule affects Business Days and the business-day unit in Add / Subtract. Timesheet weeks use ISO-week grouping; this schedule does not control that grouping.
• Holidays to exclude affects Business Days and business-day Add / Subtract only.
• The Break policy controls Work Hours & Timesheet: no automatic break, a fixed unpaid break, or manual break minutes.
• Daily overtime threshold (hours) and Weekly overtime threshold (hours) are numeric inputs. Overtime pay multiplier (label only) is informational and does not calculate wages or payroll.

Enter and manage timesheet shift rows

One shift row is created automatically. Enter its Date, Start time, and End time. Select Add shift row for another segment, or Remove row to delete a row. Manual break (min) appears only with the manual break policy.

Use multiple rows on one date for split shifts. If an end time is equal to or earlier than its start time, the segment is treated as crossing into the next day. A fixed break applies once a segment exceeds its configured threshold; manual breaks use the minutes entered on each row.

Validation and calculation limits

• Required dates and times must be valid.
• Business Days rejects an end date before the start date and ranges over 36,600 days.
• Elapsed Duration rejects an end instant before the start instant.
• Add / Subtract accepts only whole, non-negative amounts.
• At least one weekday must be selected for workday calculations.
• Invalid holiday entries and invalid timesheet dates or times stop calculation.
• Timesheet end times equal to or earlier than start times cross midnight; they are not rejected for that reason.

Date arithmetic and month-end behavior

In Add / Subtract, years are converted to 12 months. When a month result would use a day that the target month does not have, the date is clamped to the target month's last day. Business-day arithmetic skips unselected weekdays and entered holidays.

What the calculator does not apply

The tool does not fetch public holiday calendars. Only dates entered in Holidays to exclude are excluded. It does not apply employment-law, rest-period, meal-break, or overtime rules, and it does not perform payroll tax withholding or net-pay calculations.

Privacy and browser calculation

The calculator logic performs its calculations in your browser. This article does not make broader claims about how site analytics or other page activity handle entered data.

Frequently Asked Questions