Inclusive versus Exclusive (Calendar) Counting

Culture Musing

Ever encountered documents, statements, or people that to you they counted dates wrong–additional 1 day or lacking 1 month? Or maybe you were in a situation wherein you were wondering if you have to count the starting date as 1, or count the next day/month instead.

It is confusing, yes. The reason is simple, when it comes to counting calendar dates, most cultures both in times past and the present (at least our present) count days and months and years, even millenias and eons, inclusive of the starting date. There was and is no 0 (zero). We do not start counting from zero. But in other disciplines, especially where mathematics is involved, zero is equally important as any other numerals. Hence the confusion.

In this post, I’m going to give some few examples of the different between inclusive and exclusive calendar counting.


Question: If it is Sunday, what is the 7th day from now?

  • Exclusive counting: Sunday. Monday is the 1st day.
  • Inclusive counting: Saturday. Sunday is the 1st day.

Question: How many months have you worked from September to August?

  • Exclusive counting: 11 months. October is first month.
  • Inclusive counting: 12 months. September is first month.

Question: How old are you today, August 8, 2013, if you were born in the 8th of August Year of Our Lord nineteen eighty?

  • Exclusive counting: 33.
  • Inclusive counting: 34.

Cultures known to count inclusively (or in the past)

  • Hebrew culture
  • United Kingdom of Great Britain (Scotland, England, Wales) and Northern Ireland
  • Ireland
  • British Commonwealth of Nations (Australia, New Zealand, etc.)
  • East Asian Nations (China, Japan, Korea, Mongolia, etc.)
  • Some regions of Canada
  • Many European countries

Cultures that count exclusively

  • United States of America
  • Philippines (heavily influenced by the US during the colonial times)
  • The rest of Canada
  • Territories and Nations heavily influenced by or under the control of the US (and the old “US Commonwealth”)
  • Most of the countries today

Day 0? Year 0?

Logically, when counting dates, inclusive counting is the correct and proper method. We should not count from zero, we should always count from one. Zero is for where mathematical computations are involved. We do not necessarily need mathematical rules when counting calendar dates.

Have you ever encountered “Day 0” in your life? Is the first week of the year ever called “Week 0”? Of course not (unless you create your own calendar system). We do not have January 0, 2014 next year, or October 0, 2013 in the next few days. We always begin with 1 not 0.

The same reason why there was/is no Year 0 between 1 B.C. (Before Christ) and 1 A.D. (Anno Domini). From 2 BC to 2 AD, we only have 4 years, not 3 years, and definitely not 5 years. It is also for the same reason why the 3rd millenium officially started on January 1, 2001 and not on January 1, 2000.

Do you count 10, 1, 2, 3, 4, 5, 6, 7, 8, 9? Or do you count from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10? How can you count 0 when zero means nothing? You can not count what does not exist!

The Changing Times

Of course (and obviously), inclusive calendar counting is being replaced with exclusive calendar counting especially when it comes to legal. In CJK–that’s China, Japan, and Korea–they use exclusive calendar counting in legal documents and statements but they use inclusive calendar counting in other things like ages/birthdays, holidays, seasons, etc.

That is why Koreans seem to be a year older if you are used to exclusive (calendar) counting. An 18-year old Korean pop star is only 17-year old in exclusive counting. In inclusive calendar counting, the year of birth starts as 1 year old. In exclusive counting, the year of birth starts as 0 (zero, again, means nothing or does not exist–and yet you were already born!)

I can not say the same with the British Commonwealth, correct me if I’m wrong, but the Commonwealth still count calendar dates inclusive even in legal.


The sad thing, there’s no way to know if a person or a document you are reading used inclusive or exclusive calendar counting. Just remember the two calendar-counting methods and you’ll be fine. (If you correct them, then you definitely will not be fine.) Bottomline, just do the math (ironic we have to do math when mathematics has nothing to do with calendar reckoning).

You see then, inclusive calendar counting is the correct and proper method to use when it comes to counting dates. In fact, not just dates, but counting itself. We start with 1 and not 0. Going back to our example, if your year of birth was considered year 0, and zero means nothing or does not exist, then I guess you were a ghost.

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