Counting days between two dates without getting burned
Most disputes here come down to one question: do you count both ends? A Days Between Dates Calculator gives you the raw elapsed span — subtract and done. But a lease that says “notice must be given within 30 days” is often read inclusively, so the number you need is one higher than the subtraction gives you. I'd read the contract twice before trusting either number.
Working forward or backward from a known date is a different problem. The Date Plus Days Calculator adds or subtracts a day count from any date you pick, while Days From Today Calculator and Days Ago Calculator do the same thing anchored to today, which is what most people actually type into Google. And if weekends and public holidays shouldn't count at all — payroll deadlines, court filings — the Business Days Calculator is built for exactly that.
Hours, minutes, decimals: why 1:20 isn't 1.20
This trips up more people than it should. Payroll software stores time as a decimal, but your brain reads a clock face. One hour thirty minutes converts cleanly to 1.5 — half of 60 is 30, easy. One hour twenty minutes does not convert to 1.20, because 20 minutes is a third of an hour, not a fifth. It's 1.33. Multiply that gap across a two-week pay period and you can see how someone underpays a whole team without meaning to.
Two calculators fix this in either direction: Time to Decimal Calculator and Decimal Hours to Time Calculator. If you just need a quick unit swap without the decimal confusion, Minutes to Hours Calculator and Hours to Minutes Calculator handle it in one step. And for totaling an actual shift — clock in, lunch break, clock out — the Work Hours Calculator does the whole thing at once.
Age, week numbers, and counting down to something
Age math sounds trivial until you try to do it by hand and remember that February has 28 days some years and 29 in others, and that months range from 28 to 31 days depending on which one you land on. The Age Calculator handles that and gives you a clean years/months/days breakdown from a birth date. If you need the number as a single total instead — which shows up on medical intake forms more than you'd think — the Age in Days Calculator gives you that count directly.
Separately: the Week Number Calculator outputs the ISO week number, which is how a lot of European scheduling and manufacturing planning is organized (not the “week of the year” number you'd guess by counting Sundays). The Days Until Date Calculator counts down to a fixed event, whatever it is. And one thing that trips up spreadsheet formulas constantly: a shift or duration that crosses midnight will show as negative unless you handle the rollover, which is exactly what the Time Duration Calculator is built to catch.
Frequently asked questions
- How many days are there between two dates?
- Subtract the earlier date from the later one and you get the elapsed count — that's the straightforward version. Leap years complicate long spans slightly since they add a day roughly every four years. The part people actually get wrong is whether to include the start or end day; legal notice periods and rental terms frequently count inclusively, so read the wording before you rely on the raw subtraction.
- What counts as a business day?
- Monday through Friday, minus public holidays — that's the general rule, though banks and shipping carriers each have their own fine print on which holidays apply. In practice, five business days usually lands about a week later, sometimes longer if a holiday falls in that stretch.
- How do I turn timesheet minutes into decimal hours?
- Divide by 60. Forty-five minutes becomes 0.75 hours; twenty minutes becomes 0.33 hours. It's the same math every time, but doing it in your head for odd numbers like 37 minutes is where mistakes creep in.
- What exactly is an ISO week number?
- It's the numbering defined by ISO 8601, where weeks run Monday through Sunday and week 1 is whichever week contains the first Thursday of January. Because of that rule, some years have 53 weeks instead of the usual 52, and the first few days of January can technically still belong to week 52 of the previous year.
- How do you calculate hours worked when a shift crosses midnight?
- Add 24 hours to the end time before subtracting, so it's treated as belonging to the next day rather than an earlier hour on the same day. A shift starting at 22:00 and ending at 06:00 works out to 8 hours — done the naive way, subtracting straight across, you'd get negative 16, which obviously isn't right.