Date & Time calculators

A 90-day payment term is not three months, and three months is not 90 days. A 122-day project window contains only about 87 working days once weekends come out. Each of these counts answers a different question, and quoting the wrong one is how schedules slip before work even starts. Contracts overwhelmingly define terms in days precisely because days are the only unit with a fixed length.

Months are elastic in both directions. Adding one month to 31 January either overflows into March or clamps to 28 February depending on the convention applied, and the two answers differ by several days. If an agreement is expressed in months, it should say which rule governs; if it cannot, express it in days instead.

Every calculator here works in UTC internally. That is deliberate: in a local time zone, two days each year are 23 or 25 hours long, and naive subtraction across a clock change lands a day out. Anchoring to UTC removes that failure mode entirely, at the cost of one caveat — a deadline expressed in a local zone can differ by a day at the boundary, so cross-border deadlines should always name their reference zone.

The same applies to log analysis. A timestamp of midnight UTC on 1 January is the evening of 31 December across the Americas. Incident timelines assembled from systems in different zones need every entry normalised before they can be compared, which is what epoch timestamps exist to make possible.

Payroll systems want hours as decimals, so 8 hours 20 minutes is 8.33 hours. Entering 8.20 loses eight minutes, and repeated daily across a workforce that becomes a material and legally exposed underpayment. The duration and time card calculators both output decimal hours for exactly this reason.

Overtime rules add another layer. The US federal standard is weekly above 40 hours at time and a half, but several states impose a daily threshold as well, and where both apply the more generous outcome governs. Non-discretionary bonuses and shift differentials usually have to be folded into the regular rate before the premium is applied, which raises the effective overtime rate above the base wage.