Idiot Date Tools is a single-category toolbox built entirely around dates and calendars — age, duration, timezones, deadlines, holidays and more. Every tool runs instantly in your browser. No signup, no ads blocking the calculator, no data leaving your device.
30 tools, all client-side
Find the exact number of days, months and years between any two dates.
Open tool →Work out an exact age in years, months and days from a birth date.
Open tool →Live countdown to any future date, minute, hour or event.
Open tool →Count business days between two dates, excluding weekends and holidays.
Open tool →Instantly find which weekday any calendar date fell or falls on.
Open tool →Generate and print a clean monthly or full-year calendar for any year.
Open tool →Convert between calendar dates, Unix epoch time and Julian day numbers.
Open tool →Convert a time from one timezone to another in a single click.
Open tool →Compare up to five timezones side by side to find a meeting slot that works.
Open tool →Check instantly whether any year is a leap year, and why.
Open tool →Find the ISO-8601 week number for any date of the year.
Open tool →Add or subtract days, weeks, months or years from any starting date.
Open tool →Generate the next occurrence and countdown for any recurring birthday or anniversary.
Open tool →Convert dates between the Gregorian and Hijri (Islamic lunar) calendars.
Open tool →Calculate your exact retirement date from your birth date and target age.
Open tool →Work backward or forward from a deadline using working-day effort estimates.
Open tool →Browse public and bank holidays for major regions across any year.
Open tool →Find the precise age gap between any two people, in years and months.
Open tool →Estimate a pregnancy due date and current week from the last period or conception.
Open tool →Find the Western zodiac sign and date range for any birth date.
Open tool →Find the exact date of the 1st, 2nd, 3rd, 4th or last weekday of any month.
Open tool →Find the moon phase for any date, past or future, plus days to the next full and new moon.
Open tool →Find the Chinese zodiac animal and element for any birth year.
Open tool →See exactly what percentage of any year has elapsed and how many days remain.
Open tool →Find which season any date falls in, for the Northern or Southern Hemisphere.
Open tool →Find your golden birthday — the year you turn the same age as your birth date's day number.
Open tool →Find the next palindrome date — one that reads the same forwards and backwards.
Open tool →Convert a date between US, international, ISO and written-out formats instantly.
Open tool →Calculate the hours and minutes between two clock times, with optional unpaid break deduction.
Open tool →Find which decade, century and millennium any year belongs to.
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