Date & Time

Category overview

Date and time tools cover calculations whose answers change depending on reference dates and time zones, such as D-day counters, date differences, age checks, duration sums, and timestamps. The fallback content explains inclusive dates, local time, and seconds versus milliseconds where relevant.

These tools are intended for quick checks in scheduling, forms, and log debugging. When a government agency, school, or service uses a specific rule, compare the result with that rule before relying on it.

Currently showing 31 reviewed tools, including Date Difference Calculator, D-Day Calculator, Age Calculator, Time Calculator, Timestamp Converter.

Date & Time List

• Date Difference Calculator - Calculate the number of days between two dates, or the date N days from a reference date.
• D-Day Calculator - Show the days remaining until, or elapsed since, a target date based on today.
• Age Calculator - Calculate your exact age, this year's birthday status, and days until your next birthday.
• Time Calculator - Add or subtract time from a clock time, and calculate the interval between two times.
• Timestamp Converter - Convert Unix timestamps to readable dates and dates back to Unix timestamps.
• Months Between Dates Calculator - Calculate total months, days, and a year/month/day breakdown between two dates.
• Day of the Week Calculator - Find the day of the week for a date and its day difference from today.
• Leap Year Checker - Check whether a year is a leap year and how many days February has that year.
• Stopwatch - Measure time in milliseconds and record lap times.
• Countdown Timer - A countdown timer that alerts you when the set time reaches zero.
• Pomodoro Timer - A timer with 25-minute focus and 5-minute break cycles to boost concentration.
• Pregnancy Week Calculator - Calculate the pregnancy week and due date from the last menstrual period (LMP).
• Ovulation Calculator - Estimate ovulation day and the fertile window from the last period and average cycle.
• World Clock Converter - Convert a given date and time to the local time of major cities and time zones at once.
• Time Zone Converter - Convert a chosen date and time to another time zone's representation.
• Business Day Calculator - Calculate a date N business days out or the number of business days, excluding weekends.
• Week Number Calculator - Find which week of the year a date falls in, based on ISO 8601.
• Date Range Generator - Generate a list of all dates between a start and end date at once.
• Meeting Time Finder - Find times where working hours overlap across multiple time zones.
• Date Add/Subtract Calculator - Add or subtract days, weeks, months, or years from a reference date.
• Work Hours Calculator - Calculate work hours from clock-in, clock-out, and break time.
• Sleep Time Calculator - Calculate recommended bedtimes aligned to 90-minute sleep cycles based on your wake time.
• Unix Millisecond Converter - Auto-detect 10-digit second and 13-digit millisecond timestamps and convert to date/time.
• Alarm Clock - A simple alarm clock that runs in your browser and plays a synthesized beep.
• Leap Month Calculator - Check whether a lunar month is normal or leap, and find leap-month date ranges by year.
• Korean Zodiac Calculator - From a birth date, find the Korean zodiac sign by both Lunar New Year and Ipchun (solar term).
• Samjae Calculator - Determine Samjae (the three-year unlucky cycle) status from a zodiac sign and reference year.
• Zodiac Sign (Horoscope) Calculator - Find your Western zodiac sign from your solar birth date, with a personality summary.
• Korean Milestone Birthday Calculator - Calculate Korean traditional longevity celebration dates and D-days (Hwangap 60th, Chilsun 70th, etc.).
• 49-Day Memorial Calculator - Calculate Buddhist memorial dates from the first rite to the 49th-day rite, with weekdays and D-days.
• Sexagenary Cycle Calculator - Identify the sexagenary year, its symbolic animal and color, and trace years for a given cycle name.