Date Difference
Counts days, weeks, months and years between two dates, with a D-day view and business-day option.
How long between two dates, answered four ways at once: in days, in weeks, in months and years, and as a D-day count. The business-day option leaves out weekends and Korean public holidays, which is the number a deadline actually runs on.
Tuesday
Thursday
Difference
Days
51
Calendar
0y 1m 21d
Weeks
7w 2d
Business days
36
14 weekend, 1 holiday
Months (approx.)
1.7
Business days count the start day and not the end day, which is the convention every "within N business days" clause uses. One month of calendar difference is 28 to 31 days depending on which month it was, so the two rows will not agree — that is arithmetic, not a bug.
D-day
D-51
Korean D-day counting puts the event itself at D-day and the day before at D-1, so there is no D-0.
How to use it
Put in the two dates
Order does not matter — the difference is reported as a magnitude with the direction stated. Both dates are read in your own timezone.
Decide whether the end date counts
A hotel stay from the 1st to the 3rd is two nights; a course running the 1st to the 3rd is three days. Both readings are correct, so the tool shows both rather than picking one.
Turn on business days if it is a deadline
This drops Saturdays, Sundays and Korean public holidays including 대체공휴일. It is the difference between "thirty days" and "the day the paperwork is actually due".
Common questions
Why does the months figure look odd?
Because months are not all the same length. From 31 January to 28 February is one month by the calendar and 28 days by the clock, and any tool that gives a single number has quietly chosen one. Both are shown here.
Are leap years handled?
Yes, including the century rule: 2000 was a leap year and 1900 was not. Day counts are exact calendar arithmetic rather than an approximation of 365.25 days a year.
Does it know about 임시공휴일?
No. Substitute holidays follow a rule and are computed; temporary holidays are declared by decree, sometimes weeks in advance, and there is nothing to compute. Take them off by hand when one falls in your range.
Feed it from
Date Add & Subtract
Adds or subtracts days, weeks, months or years from a date, optionally skipping weekends and holidays.
Unix Timestamp Converter
Converts between epoch seconds, milliseconds, ISO 8601 and human dates in any timezone.
Business Day Counter
Counts working days between dates, or finds the date N working days out, excluding weekends and holidays.
Time Duration Calculator
Adds and subtracts hh:mm:ss durations, totals a column of times and converts to decimal hours.
Next
These accept what this tool produces, so the result can go straight in.
Business Day Counter
Counts working days between dates, or finds the date N working days out, excluding weekends and holidays.
Date Add & Subtract
Adds or subtracts days, weeks, months or years from a date, optionally skipping weekends and holidays.
Korean Age Calculator
Works out your 만나이, 연나이 and the old 세는나이 from a birth date, on any reference day.
Korean Public Holidays
Lists public holidays and substitute holidays for a year, including the lunar-dated ones, as a calendar or ICS.
CSV Viewer
Opens a large delimited file with type detection, column stats and sorting, without loading it all into memory.
Currency Converter
Converts between about thirty currencies at the ECB’s daily reference rates, crossed through the euro, or at a rate you type in.