Date & Time

Date and time utilities

Calendar arithmetic misleads because the calendar refuses to behave like a number line: months run from 28 to 31 days, February changes every fourth year, and century years obey their own rule. The trouble compounds because the question being asked changes what the calendar owes you — a length, a landing date, an amount of working time someone will actually be at their desk. Each tool here settles one of those forms without pretending the calendar is tidier than it is.

The Date Difference Calculator measures the span between two dates in days, weeks, months and years, applies the full Gregorian leap-year rules — so a span crossing February 2024 measures 366 days where 2023 measures 365 — and lets you count the end day inclusively when the wording calls for it. The Date Calculator moves a date by an offset of years, months, weeks and days, clamping the month end the way contracts expect — January 31 plus one month lands on February 28, or the 29th in a leap year — and shows the weekday that results. The Working Days Calculator counts the business days inside a span under a weekend convention you choose and a holiday list you supply, ignores holidays that fall on the weekend rather than subtracting them twice, and splits the span into working, weekend and holiday days so the answer shows its own work. The Unix Timestamp Converter steps outside the calendar entirely, translating epoch counts into readable dates and back, detecting from a value's length whether it is seconds or milliseconds and displaying its guess so you can overrule it on ambiguous values.

Between them they answer the forms the question takes: how long, what date, how much of the span is working time — and, in raw seconds, when exactly.

Every tool below runs entirely in your browser — no signup, no downloads, no data leaves your device.