Date & Time Calculators
Deadlines, due dates and day counts are easier when the calendar does the math. Count days between two dates, jump forward by business days, check a week number, or plan a meeting across time zones — all in a click.
Date Calculator
Add or subtract days, weeks, months and years from any date.
Open toolDate Difference Calculator
The exact days, weeks and months between two dates.
Open toolBusiness Days Calculator
Count working days between dates, skipping weekends and holidays.
Open toolWeek Number Calculator
Which week of the year any date falls in, using ISO week numbers.
Open toolCountdown Timer
A live countdown to your date — days, hours, minutes and seconds to go.
Open toolTime Zone Converter
Convert a time between time zones around the world.
Open toolTime Duration Calculator
Add and subtract times, or find the duration between two clock times.
Open toolBusiness Date Calculator
Jump forward or back by a number of business days from a start date.
Open toolWeekday Calculator
The day of the week for any date, past or future.
Open toolRoman Numeral Converter
Convert numbers to Roman numerals — and Roman numerals back to numbers.
Open toolDate Pattern Calculator
Find repeating dates, like every second Friday or the third Monday of the month.
Open toolMeeting Planner
Find meeting times that work across multiple cities and time zones.
Open toolSunrise and Sunset Calculator
Sunrise, sunset and day length for your location and date.
Open toolMoon Phase Calculator
The moon's phase and illumination for any date.
Open toolDays From Now Calculator
The date 30, 90 or any number of days, weeks or months from a start date — with the weekday.
Open toolWeeks Between Dates Calculator
Whole weeks and remaining days between two dates, plus the total day count.
Open toolMonths Between Dates Calculator
Whole months and remaining days between two dates, plus the total day count.
Open toolLeap Year Checker
Is a year a leap year? Check any year, see why, and find the previous and next leap years.
Open toolDay of the Year Calculator
Which day of the year a date is (1–366) — and the reverse: turn a day number back into a date.
Open toolDates, deadlines and day counts
Day counts sound simple until a contract, a visa window or a project plan depends on them. Calendar days, business days and exact date differences are three different answers to what looks like one question, so these tools keep them separate: count working days with the business-day tools (US federal holidays can be skipped), measure an exact span with the Date Difference Calculator, and move a date forward or back with the Date Calculator.
All date math here is done in UTC, so daylight-saving changes never add or steal a day, and leap years are handled exactly. Planning something ahead? The Countdown Timer ticks live to any date you set, and the week tools give ISO week numbers and weekdays for schedules, timesheets and school terms.
Forward-looking questions have their own tools: the Days From Now Calculator jumps a set number of days, weeks or months ahead with one-tap presets, while the Weeks Between Dates Calculator and Months Between Dates Calculator break a span into whole weeks or months plus the days left over. The Day of the Year Calculator converts between a date and its ordinal day (and back), and the Leap Year Checker settles any year — including the century cases like 2100 that break the simple divisible-by-4 rule.