Date & Time tools
Handle recurring date calculations — D-Day countdowns, age, date differences, business days — instantly in the browser, with the timezone and formula stated on each page.
Popular date tools
D-Day Calculator — Date Calculator
calculates days remaining until or elapsed since a target date.
Date Difference Calculator — Date Calculator
calculates the number of days between two dates.
Age Calculator — Date Calculator
calculates age and days lived from a birth date.
Korean Age Calculator — International (Man) Age
Enter a birth date to get the Korean legal (international) age under the 2023 age-unification law, and see how it differs from traditional Korean counting age.
Weekday Calculator — Date Calculator
finds the weekday for a specific date.
Week Number Calculator — Date Calculator
finds the ISO week number and day of year for a date.
Date Add/Subtract — Base Date ± Days
Add or subtract days from a base date and calculate the resulting date and weekday.
Business Days Calculator — Weekdays Excluding Weekends and Holidays
Calculate weekdays between two dates while excluding Saturdays, Sundays, and entered holiday dates.
Timezone Converter — UTC Offset Time Conversion
Convert a date and time from one UTC offset to another UTC offset.
World Clock — Current Time in Major Cities
Check current time for Seoul, London, New York, Los Angeles, Tokyo, and other common regions.
12/24 Hour Converter — AM/PM and Military Time
Convert between 12-hour AM/PM time and 24-hour time.
Time Duration Calculator — HH:MM Time Calculator
Add multiple HH:MM durations and calculate total time and total minutes.
Time Difference Calculator — HH:MM Time Calculator
Calculate the difference between a start time and an end time.
Countdown Calculator — Event Date Calculator
calculates time remaining until a target date and time.
Anniversary Calculator — Event Date Calculator
calculates years elapsed and days until the next anniversary.
100 Days Calculator — Event Date Calculator
calculates the 100th day from a start date.
Pregnancy Week Calculator — Estimated Date Calculator
estimates current gestational age and due date.
Pregnancy Due Date Calculator — Estimated Date Calculator
estimates a due date from the last menstrual period.
Ovulation Calculator — Estimated Date Calculator
estimates ovulation date and fertile window from average cycle length.
Zodiac Sign Calculator — Date Based Calculator
finds the Western zodiac sign from a birthday.
Korean Zodiac Calculator — Date Based Calculator
calculates the twelve-animal zodiac from birth year.
CSAT D-Day Calculator — Date Based Calculator
calculates days remaining until the 2027 Korean CSAT.
Military Discharge Date Calculator — Date Based Calculator
calculates an estimated discharge date from enlistment date and service months.
Timer — Minute and Second Countdown
Enter minutes and seconds to run a countdown timer in your browser.
Stopwatch — Measure Elapsed Time
Run a browser stopwatch with start, pause, and reset controls.
Moon Phase Calculator — Today's Moon, Illumination, Full Moon Dates
Enter a date to get the moon phase (new, first quarter, full, last quarter), illumination percent, a monthly phase calendar, and the next full moon date.
Sunrise Sunset Calculator — Sun Times by City or Coordinates
Calculate sunrise, sunset, solar noon, and day length for any date and latitude/longitude using the NOAA solar position equations. Korean city presets included.
Meeting Planner — Multi-City Time Zone Overlap Finder
Pick up to five cities (Seoul, London, New York, and more) and see a 24-hour table of local times with working-hours (09:00–18:00) overlap highlighted.
Calendar Generator — Printable Monthly and Yearly Calendar with Korean Holidays
Pick a year and month to generate a printable monthly or yearly calendar with Korean public holidays (including substitute holidays) marked.
Korean Lunar-Solar Calendar Converter — Leap Months and Ganji (Sexagenary Cycle)
Convert between the Korean lunar calendar and the Gregorian calendar with leap-month handling and the ganji (sexagenary cycle) for year, month, and day. Supports 1000–2050.
Son-eomneun-nal Calendar — Korean Moving Lucky Days
Calculate Korean son-eomneun-nal days (lunar days ending in 9 or 0) for a selected Gregorian month in your browser.
RRULE Generator — Recurring Calendar String Builder
Build an iCalendar RRULE string from frequency, interval, count, until date, and weekdays in your browser.
Workday Countdown — Business Days Until a Target
Calculate remaining weekdays/business days from today to a target date, with optional holiday exclusions.
Moving Checklist Generator — Browser Schedule Tool
generates a D-30 through D+7 moving checklist from a move date. Input is processed only in your browser.
ICS Event Generator — Browser Schedule Tool
generates an iCalendar .ics event from title, start date/time, and duration. Input is processed only in your browser.
Project Backward Scheduler — Browser Schedule Tool
works backward from a deadline to generate milestone dates. Input is processed only in your browser.
Age and Zodiac Compare — Browser Schedule Tool
compares legal age difference and Korean zodiac animals for two birth dates. Input is processed only in your browser.
Tenure Calculator — Browser Schedule Tool
calculates tenure duration and time until next anniversary from a hire date. Input is processed only in your browser.
Jet Lag Planner — Browser Time Planning Tool
generates a sleep and light exposure adjustment plan from origin and destination UTC offsets. Input is processed only in your browser.
Meeting Invitation Message Generator — Browser Time Planning Tool
generates meeting invitation copy and calendar notes from meeting time and agenda. Input is processed only in your browser.
Timezone Overlap Heatmap — Browser Time Planning Tool
shows working-hour overlap across multiple UTC offsets as a 24-hour table. Input is processed only in your browser.
FAQ
How is age calculated?
The age tools use international age: current year minus birth year, minus one if the birthday has not yet passed. The Korean age tool also explains the counting-age difference.
How does the D-Day countdown work?
It subtracts today from the target date to show days remaining or elapsed, using your browser’s local timezone.
Do business-day tools only skip weekends?
Weekends are skipped by default, and some tools let you add specific holidays to exclude.
Are entered dates sent to a server?
No. Date calculations run in the browser and input is not sent to a server.