Date and time calculators
Work with calendar dates and clock times without turning months into averages or hiding how overnight intervals are handled.
Calculators in this section
Compare dates or add and subtract calendar units.
Business daysCount weekdays and optional US federal holidays.
Time durationFind hours and minutes between two clock times.
Time cardTotal weekly shifts and subtract unpaid breaks.
Age calculatorFind calendar age on today or another date.
Military timeConvert between 12-hour and 24-hour clock times.
Decimal timeConvert hours and minutes to decimal hours and back.
Calendar units stay calendar units
Months are added as months, leap days stay visible, and business-day counts state exactly which endpoints and holidays are included.
Arithmetic, not policy
The time-card and business-day tools calculate the values you enter. They do not decide payroll eligibility, legal deadlines or an organization’s holiday policy.
Which one answers your question
For a gap between two dates, or a date moved forward or back, use the date calculator: it counts in complete years and months and also gives the total in days. When the gap has to skip weekends, the business days calculator does the same job on weekdays only, with US federal holidays removed if you ask for it. For someone’s age on a given day, the age calculator applies the same calendar rules to a date of birth.
For clock time rather than calendar dates, the time duration calculator measures one interval and handles a shift that crosses midnight, while the time card calculator totals a full week with unpaid breaks taken out. The last two pages convert notation rather than measuring anything: 12-hour to 24-hour, and hours and minutes to the decimal figure a timesheet or an invoice expects.
Frequently asked questions
Which time zone do date calculations use?
Date-only calculations use calendar dates rather than a clock or time zone. Clock-duration tools use the times exactly as entered, so neither kind of calculation shifts when you travel or when the clocks change.
Are US federal holidays always excluded?
No. The business-day calculator excludes them only when you enable that option, and it knows the 11 federal holidays and their observed dates. State holidays, school breaks and company days are not included and cannot be added.
Which tool should I use for a work week?
The time duration calculator measures one interval between two clock readings. The time card calculator totals a whole week of shifts with unpaid breaks subtracted from each day, and splits the hours at a weekly threshold you choose.
Is anything I enter stored or uploaded?
No. Every calculation on these pages runs in your browser. Dates, shift times and totals stay in the page, are never sent to a server, and disappear when you close the tab.