Updated July 18, 2026
Tracking work hours accurately keeps pay correct and scheduling sane. This guide covers the timekeeping conversions that come up most and the tool for each.
Hours and durations
The foundation of any timesheet is the time between clock-in and clock-out. The Time Duration Calculator returns hours and minutes between two times, including overnight shifts, while the Add or Subtract Time Calculator adds or subtracts hours and minutes from a starting time and flags when the result rolls into another day.
Decimal hours for payroll
Payroll systems multiply a pay rate by decimal hours, not hours and minutes, so 7 hours 30 minutes becomes 7.50. Getting this conversion right prevents under- and over-payment. The Decimal Hours Calculator converts H:MM to decimal and back; remember the common marks: 15 minutes is 0.25, 30 is 0.50, 45 is 0.75.
Military (24-hour) time
24-hour time removes the AM/PM ambiguity that causes scheduling mistakes - 1300 is unmistakably 1:00 PM. It's standard in healthcare, aviation, the military and many timesheets. The Military Time Converter converts between 24-hour and 12-hour formats in both directions.
Time zones
Coordinating across locations means converting time zones, and daylight saving makes it tricky because the offset changes through the year. The Time Zone Converter converts a date and time between major world zones and handles daylight-saving automatically, so a 9 AM call in New York shows correctly for a colleague in London or Tokyo.
Accuracy tips
Two habits prevent most timesheet errors: convert to decimal hours before applying a pay rate, and double-check overnight or cross-zone entries where the date can change. For recurring schedules, settle on one format (usually 24-hour) to remove ambiguity, and round consistently according to your employer's policy.
One shift, four conversions
A single shift usually has to pass through every conversion on this page before it reaches a paycheck. Take a shift logged as 9:00 AM to 4:45 PM with a 30-minute lunch. Written in 24-hour time, that is 09:00 to 16:45, which removes any AM/PM ambiguity before you do the subtraction. The raw duration is 7 hours 45 minutes; subtract the 30-minute lunch and you get 7 hours 15 minutes worked. Converting the 15 leftover minutes to a decimal (15 / 60 = 0.25) turns that into 7.25 hours, the figure a payroll system actually multiplies by an hourly rate. If the same employee needs to confirm a scheduling call with a colleague three time zones east, the 16:45 clock-out converts through UTC and lands at a different local hour depending on whether either zone is currently observing daylight saving, which is exactly why the time zone tool checks the date, not just the offset.
Rounding, the step nobody mentions until a paycheck is short
Everything above assumes the punches themselves are exact. Often they aren't, and lawfully so. Under 29 CFR 785.48(b), an employer may record time to the nearest 5 minutes, tenth of an hour, or quarter hour, so long as the rounding averages out instead of consistently trimming pay. Quarter-hour rounding produces the famous 7-minute boundary: a 7:52 AM arrival becomes 7:45 on the record, while 7:53 becomes 8:00. Knowing which system your employer uses turns a confusing pay stub into a checkable one. Convert your own unrounded punches with the tools on this page, compare against the official total, and expect small differences that wander in both directions. What you should not see is a discrepancy that always favors the same side; the regulation conditions the whole practice on it evening out over time.
Auditing one pay period, in order
The workflow that catches errors fastest runs the conversions in a fixed sequence rather than ad hoc. First put every punch into 24-hour form so AM/PM mistakes die early. Second, total each day in minutes, subtracting only unpaid breaks. Third, convert daily totals to decimal hours and sum the week. Only then compare against the stub. Done in that order, a discrepancy points at one specific step; done all at once in your head, a discrepancy points everywhere.
Picking a timekeeping system: what each one gets wrong
The conversions above are the same no matter how punches get recorded, but the recording method decides how many errors you have to catch. Every system in common use trades convenience against a specific failure mode.
| System | Typical cost | Where it breaks |
|---|---|---|
| Paper timesheet | Free | Written from memory at week's end; math errors; no audit trail |
| Punch clock / badge swipe | Low, one-time | Buddy punching; missed punches need manual fixes |
| Web or phone app | Per user, monthly | Dead battery, dead zone, and forgotten clock-ins; GPS raises privacy questions |
| Biometric clock | Highest upfront | Consent laws in some states (Illinois's BIPA is the strictest); wet or worn fingerprints misread |
Paper deserves a specific warning. A timesheet filled out Friday afternoon is a memory test, not a record, and the errors do not cancel out; people round their own arrival times down and departure times up in reassuringly small increments that compound over a year. If paper is what your workplace uses, write times down at the moment they happen and total them with the time card calculator instead of doing the arithmetic by hand at the bottom of the sheet. The clock-based systems fix the memory problem and introduce the missed-punch problem, which is why every one of them pairs with an edit process. Edits are lawful when they correct the record to match reality. An edit trail that only ever shortens shifts is a different conversation.
How long the records have to exist
Federal recordkeeping rules put specific shelf lives on all of this. Under 29 CFR Part 516, payroll records themselves must be kept at least three years, and the documents wage computations are based on, including time cards, work schedules, and records of additions or deductions, must be kept at least two. The records must show the hours worked each day and the total for each workweek, not just a pay-period lump. For an employee, the practical takeaway is that the punch-level detail behind a paycheck from last year should still exist somewhere, and you can ask for it. Keeping your own copy is easier: a photo of the paper sheet, a screenshot of the app's weekly summary, or an export from the time card tool here costs nothing and settles most disputes before they start.
Which breaks come out of the total, and which never should
Break deductions are where a correctly recorded shift still turns into a wrong paycheck. Federal rules split breaks into two kinds. Short rest breaks, the 5-to-20-minute coffee or smoke variety, count as hours worked and are paid time under 29 CFR 785.18; they should never be subtracted from a timesheet. Bona fide meal periods, ordinarily 30 minutes or longer, are unpaid under 785.19, but only when the employee is actually relieved of duty. Eating a sandwich at the register while covering the counter is work, and a system that auto-deducts 30 minutes for lunch regardless of whether lunch happened is one of the most common sources of underpayment there is. The fix is boring and effective: record the real break, not the scheduled one. When you total a week in the time card calculator, enter only the breaks where you were genuinely off duty, then compare that figure against a stub that used the auto-deduction. A gap of 30 minutes a day is 2.5 hours a week, which at $18 an hour is $45 a week and over $2,000 a year.
The two nights a year the clock itself moves
Daylight saving time creates two shifts a year where a wall clock and an hour count disagree. In 2026 the change happens on March 8, when 2:00 AM jumps to 3:00 AM, and November 1, when 2:00 AM repeats. An overnight worker scheduled 11:00 PM to 7:00 AM works 7 actual hours on the March night and 9 on the November night, and the FLSA requires pay for hours actually worked, so the paycheck should reflect 7 and 9, not 8 and 8. Timekeeping software that stores punches in UTC handles this correctly without anyone noticing. Systems that store local wall-clock times, and every paper timesheet ever filled out, quietly get both nights wrong in the same direction as the schedule. If you work overnights, those two dates are worth a calendar reminder and a one-minute check of the stub that follows.
All calculators on this site
- Time Calculator - Hours worked between a start and end time, minus breaks.
- Hours Calculator - Add up daily hours into a weekly total with pay.
- Time Card Calculator - A full week of clock-in/out times with daily and weekly totals.
- Overtime Calculator - Overtime pay at 1.5× or 2× your regular rate.
- Date Calculator - Days between dates, or add and subtract days.
- Time Zone Converter - Convert a time between any two time zones.
- Military Time Converter - Convert between 24-hour and 12-hour time.
- Decimal Hours Calculator - Convert hours:minutes to decimal and back.
- Add or Subtract Time Calculator - Add or subtract hours and minutes from a time.
FAQs
What are decimal hours?
Minutes expressed as a fraction of an hour - 30 minutes is 0.50 - used by payroll.
How does 24-hour time work?
Hours run 00 to 23 with no AM/PM; 1300 is 1:00 PM.
How do I handle overnight shifts?
Use the duration tool's next-day option so the hours calculate correctly.
Does the time-zone tool handle daylight saving?
Yes - it uses the current rules for the chosen date.
Why convert to decimal before paying?
Payroll multiplies the rate by decimal hours, not hours and minutes.
Is quarter-hour rounding legal?
Yes, under 29 CFR 785.48, as long as the rounding averages out over time instead of consistently trimming pay in one direction.
How long must an employer keep time records?
Under 29 CFR Part 516, payroll records must be kept at least three years and time cards at least two, showing hours worked each day and each workweek.
Can an employer edit my punches?
Yes, to correct the record so it matches hours actually worked. Edits that only ever shorten shifts are a red flag; keep your own copy of your times.
How does daylight saving time affect an overnight shift?
Pay follows actual hours worked. In 2026 an 11 PM to 7 AM shift runs 7 hours on March 8 and 9 hours on November 1, not 8 on each.