Date & Time Calculators

Calendar math is deceptively tricky: leap years, months of different lengths, daylight saving time. These tools handle all of it — count the days to a deadline, find an exact age, add days to a date or schedule a call across time zones — without a single off-by-one error.

Date math looks trivial until it costs you something real: a lease that ends a day earlier than you counted, a visa window measured in exact days, a deadline that lands on a weekend nobody checked. Start with the everyday pair — days between two dates for spans, add-or-subtract for deadlines ('what is 90 days from today' answers itself here, weekends included). The minute timers keep honest intervals beside them, from a one-minute breather to a full hour, and the countdown holds a date you're waiting for. When a booking is involved, nights and days stop being the same thing: a March 10 to March 15 stay is five nights but six calendar days — and hotels bill the nights.

House rules apply throughout: the arithmetic runs in your browser, nothing you type is stored, and each page shows the rule it uses — inclusive or exclusive counting, calendar months versus 30-day months — so an unexpected number always arrives with its reason attached.