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==Explanation==
 
==Explanation==
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When abbreviating the date into numerical form, {{w|Date format by country|various areas of the world}} tend to list the year, month, and day in different orders (as well as with different delimiting symbols), which can cause confusion particularly when the day value is 12 or lower allowing it to be easily interpreted as the month and vice versa. As a {{w|public service announcement}}, this comic states that there is in fact one international standard for writing numeric dates, set by the {{w|International Organization for Standardization}} in its {{w|ISO 8601}} standard: YYYY-MM-DD.
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{{w|Public service announcement}}: Two commonly used date formats are {{w|Date format by country|dd.mm.yyyy and mm/dd/yyyy}} (the symbols separating the values, as well as the year being 2 or 4 digits notwithstanding). These differences are often causes for debate. However, the comic explains that the {{w|International Organization for Standardization}} (ISO) has standardized dates in the yyyy-mm-dd format, in its {{w|ISO 8601}} standard.
  
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The comic then proceeds to list several discouraged ways of writing out the date of the comic's publication, as they do not match the standard. It begins with several commonly used ones in countries around the world but then begins to list increasingly uncommon ways, ranging from strange (Roman numerals) to quirky (binary, Unix time) to essentially impossible (painting the numbers onto a black cat).
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The comic then lists many formats as "discouraged". This list starts with commonly used formats, which include the two above as well as other commonly used ones, such as dd/mm/yy. However the list then starts listing formats ranging from uncommon to absurd, such as writing the date partly in Roman numerals and painting the date in m-d-yy format with white paint onto a hissing black cat.
  
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The title text provides a perfect example of the kind of ambiguity that can arise when non-standard formats are used. The ISO standard was in fact published on 1988-06-05 and amended on 2004-12-01. This is mentioned in the title text in MM/DD/YY format; however, there is no way to naturally figure this out, particularly with the second date.
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The ISO standard was published (to use yet another date format) on 5 June 1988 and amended on 1 December 2004, two dates given in the title text in mm/dd/yy format. Since the day values are less than 13, the format used demonstrates its ambiguity; it could be interpreted as other dates given in dd/mm/yy format (the first also as 6 May; the last as no less than five other dates as well. In both cases the century is not determined). The dates are clearly not written in ISO 8601 format, contradicting the advice in this comic, adding a level of metahumor.
  
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With the year truncated to two digits and all three numbers at 12 or lower, the date referring to December 1, 2004 (the digits pairs 12, 01 and 04) has a number of misinterpretations. Usually 12<sup>th</sup> Jan '04 (if written as US-style but read as European, or vice-versa) but with ISO-influenced "YY MM DD" ordering as one side or other of the misunderstanding it can easily become the 12<sup>th</sup> day of April 2001, the 4<sup>th</sup> day of December 2001 and the 4<sup>th</sup> of January 2012. It takes two such communication errors to 'become' the 1<sup>st</sup> day of April 2012.
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Date formats was again the subject in [[1340: Unique Date]].
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Date formats were again the subject in [[1340: Unique Date]] and [[2562: Formatting Meeting]].
 
  
 
The other mentioned formats are:
 
The other mentioned formats are:
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|-
 
|-
 
| 02/27/2013
 
| 02/27/2013
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| MM/DD/YYYY, used mostly in the [https://www.trustedtranslations.com/blog/how-are-dates-written-in-different-countries United States, Belize and Micronesia].
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| MM/DD/YYYY, used mostly in the US.
 
|-
 
|-
 
| 02/27/13
 
| 02/27/13
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| MM/DD/YY, same as above but with the year shortened to two digits.
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| MM/DD/YY
 
|-
 
|-
 
| 27/02/2013
 
| 27/02/2013
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| DD/MM/YYYY, used variously in South America, Canada ({{w|Date_and_time_notation_in_Canada|officially uses ISO 8601}}), Australia, New Zealand and much of Europe.
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| DD/MM/YYYY, used e.g. in South America, Canada ({{w|Date_and_time_notation_in_Canada|officially uses ISO 8601}}), Australia, New Zealand and Europe.
 
|-
 
|-
 
| 27/02/13
 
| 27/02/13
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| DD/MM/YY, same as above but with the year shortened to two digits.
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| DD/MM/YY
 
|-
 
|-
 
| 20130227
 
| 20130227
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| YYYYMMDD, same as ISO 8601 without delimiting punctuation. Allowed by the standard. Technically not ambiguous but is hard to read as a date at first glance.
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| YYYYMMDD, also allowed in ISO 8601
 
|-
 
|-
 
| 2013.02.27
 
| 2013.02.27
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| YYYY.MM.DD, used in Japan, South Korea and Hungary. Same as ISO 8601 except with different punctuation.
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| YYYY.MM.DD, used in Japan
 
|-
 
|-
 
| 27.02.13
 
| 27.02.13
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| DD.MM.YY, used in Germany, Russia, and others.
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| DD.MM.YY, used e.g. in Germany, Russia
 
|-
 
|-
 
| 27-02-13
 
| 27-02-13
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| DD-MM-YY, used in Denmark, Netherlands, Indonesia, India, Bangladesh, and others.
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| DD-MM-YY, used in Denmark, Netherlands, Indonesia, India, Bangladesh, etc.
 
|-
 
|-
 
| 27.2.13
 
| 27.2.13
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| D.M.YY. It is common in several areas to abbreviate the month or day to a single digit and drop the leading zero when possible.
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| D.M.YY
 
|-
 
|-
 
| 2013. II. 27.
 
| 2013. II. 27.
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| YYYY. MM. DD., with month as {{w|Roman numerals}}, used in Hungary. In this format, February and November are prone to be confused with each other: "II" vs. "11".<br/>Similar formats with the opposite ordering (27. II. 2013) existed historically in various European countries like France, Germany and Italy.  
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| YYYY. MM. DD., with month as {{w|Roman numerals}}, used in Hungary.
 
|-
 
|-
 
| <sup>27</sup>⁄<sub>2</sub>-13
 
| <sup>27</sup>⁄<sub>2</sub>-13
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| <sup>D</sup>⁄<sub>M</sub>-YY, traditional format in Denmark, Norway and Sweden
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| <sup>D</sup>⁄<sub>M</sub>-YY, traditional format in Sweden
 
|-
 
|-
 
| 2013.158904109
 
| 2013.158904109
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| Year and decimal fraction of year. 0.158904109 is a decimal approximation of 58/365, with February 27 being the 58th day of the year. This format may be easier to read for computers/programs in some contexts, but is difficult for humans to interpret.
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| Year and decimal fraction of year – 58/365, February 27 being the 58th day of the year. This representation marks the end of that day. Also allowed in ISO 8601. It is not rounded correctly 58/365 = 2013.1589041096.  
 
|-
 
|-
 
| MMXIII-II-XXVII
 
| MMXIII-II-XXVII
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| The ISO 8601 standard but written in Roman numerals. Never used as a traditional standard anywhere as it is hard to read, parse, and interpret for no benefit.
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| Year-month-day in Roman numerals
 
|-
 
|-
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| MMXIII <sup>LVII</sup>⁄<sub>CCCLXV</sub>
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| MMXIII [and] LVII [over] CCCLXV
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| Year followed by its partial fraction 57/365, all in Roman numerals. Equally useless as the above. As a note, apparently this 'standard' is different from the decimal fraction two rows above, as the decimal fraction notation uses the ''end'' of the day (first day of the year is 1/365 while the last is 365/365), while this uses the ''beginning'' (first day is 0/365 and last is 364/365).
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| Year and ''57''/365. This representation marks the start of the day, which is 57 days after the year started.
 
|-
 
|-
 
| 1330300800
 
| 1330300800
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| {{w|Unix time|UNIX Timestamp}}, a standard method of storing absolute time in many computer systems and defined as the number of seconds since 00:00:00 on 1970-01-01 (UTC). The Unix time listed here appears to mistakenly be for '''2012'''-02-27, which is also mentioned by [[Randall]] in the original transcript. The Unix Timestamp for 2013-02-27 would be 1361923200.
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| {{w|Unix time|UNIX Timestamp}}, but for '''2012'''-02-27. This refers to [http://blog.xkcd.com/2012/02/27/geohashing-2/ geohashing] done by Randall at this date.
 
|-
 
|-
 
| ((3+3)×(111+1)-1)×3/3-1/3<sup>3</sup>
 
| ((3+3)×(111+1)-1)×3/3-1/3<sup>3</sup>
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| A useless format where the numbers 2013, 2, and 27 written as needlessly long arithmetic expressions using just the digits 1 and 3. For additional confusion, the values are delimited by slashes, enabling confusion with the fraction bar.  (If evaluated literally, the entire expression evaluates to 670.963, or 671 minus one twenty-seventh.)
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| Year/month/day with the parts written as arithmetic expressions, using just the digits 1 and 3. (The slashes are not to be interpreted as fraction lines.)
 
|-
 
|-
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| <span style="position:absolute;">&nbsp;&nbsp;&nbsp;2</span><span style="position:absolute;">&nbsp;&nbsp;27</span>2013
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| 27 [''on''] 02 [''on''] 2013
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| A nearly impossible to read date "format" that can be considered a parody "compromise" between different formats: rather than argue about the order in which the year, month, and day should be, they are simply all written on top of each other. As a "bonus", there is also no arguing over which separator character to use.
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| An obfuscated date format not used ordinarily. This can be considered a compromise between the different formats: since we cannot agree on which position in the date the day, month and year parts shall be, we just write them all in the same place; we don't even need separators, which we cannot agree on either. On the other hand, reading it gets somewhat tricky...
 
|-
 
|-
 
| 10/11011/1101
 
| 10/11011/1101
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| The US mm/dd/yy format in {{w|Binary number|binary}}, corresponding to 2/27/13. Never used for obvious reasons.
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| Month/day/year in {{w|Binary number|binary}} = 2/27/13.
 
|-
 
|-
 
| 02/27/20/13
 
| 02/27/20/13
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| MM/DD/CC/YY, where CC stands for century. This format is never used.{{Citation needed}} Note that while months and days count starting from 1, centuries and years in this format count from 0 for extra confusion. But the CC value is widely used on many operating systems to distinguish between the 20th and 21st century, represented by the values "19" and "20" because 1950 belongs to the 20th century.
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| Month/Day/Century (counting from 0 and not from 1)/Year.
 
|-
 
|-
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| <table style="display: inline-table; line-height: 0.6em; align: middle; text-size-adjust: none;"><tr style="font-size:7pt; text-align: center"><td>2</td><td>3</td><td>1</td><td>4</td><td></td></tr><tr style="text-align: center"><td>0</td><td>1</td><td>2</td><td>3</td><td>7</td></tr><tr style="font-size:7pt; text-align: center"><td>5</td><td></td><td>67</td><td></td><td>8</td></tr></table>
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| 0 [2,5] 1 [3] 2 [1,6,7] 3 [4] 7 [8]
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| An obfuscated format where the small numbers indicate the positions where the respective large digits should be placed. In this reading, 0 is used at positions 2 and 5, 1 is used on position 3, etc. Coincidentally or not, positions 1 to 4 (the year) being all placed above their digits and 5 to 8 (month and day) below; the result being 20130227
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| The large digits are to be placed at the positions listed above and below: 0 is used at positions 2 and 5, 1 is used on position 3, etc.; the result being 20130227
 
|-
 
|-
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| [A hissing black cat with "2-27-13" painted on it]
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| ''A cat with'' "2-27-13" ''painted on it, going'' HiSSSS
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| In Western cultures, black cats and the number 13 are associated with bad luck. The cat might also just be angry that someone covered it in paint.
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| In Western cultures, black cats and the number 13 are associated with bad luck. The cat might also just be angry that someone painted an unstandardized date on it. The cat's "Hissss" could be a reference to timestamp formats in {{W|PHP}} web programming, where the desired date format is generally followed by [http://dk1.php.net/manual/en/function.date.php "H:i:s"], the standard 24-hour time format. That would explain the specifically lowercase "i" in the cat's hiss. It could also be a reference to {{W|LOLcat|LOLcats}} as in [[262: IN UR REALITY]].
 
|}
 
|}
  
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:*2013.158904109
 
:*2013.158904109
 
:*MMXIII-II-XXVII
 
:*MMXIII-II-XXVII
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:*MMXIII <sup>LVII</sup>⁄<sub>CCCLXV</sub>
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:*MMXIII [and] LVII [over] CCCLXV
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:*1330300800
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:*1330300800 [This is the UNIX time for ''2012''-02-27, Randall.]
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:*((3+3)×(111+1)-1)×3/3-1/3<sup>3</sup>
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:*((3+3)×(111+1)-1)×3/3-1/3<sup>3</sup> [the numbers 2013, 02, and 27 written overlapping each other]
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:*<span style="position:absolute;">&nbsp;&nbsp;&nbsp;2</span><span style="position:absolute;">&nbsp;&nbsp;27</span>2013 [the numbers 2013, 02, and 27 written overlapping each other]
 
 
:*10/11011/1101
 
:*10/11011/1101
 
:*02/27/20/13
 
:*02/27/20/13
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:*<sup><sup>2</sup></sup>0<sub><sub>5</sub></sub><sup><sup>3</sup></sup>1<sup><sup>1</sup></sup>2<sub><sub>67</sub></sub><sup><sup>4</sup></sup>37<sub><sub>8</sub></sub>
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:*[A black, hissing cat with 2-27-13 written on it.]
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:*[A black cat with 2-27-13 scrawled across its body in dripping white paint.]
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:*[The following is the last entry] 2 3 1 4 0 1 2 3 7 5 67 8
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:**Cat: ''Hissss''
 
  
 
{{comic discussion}}
 
{{comic discussion}}
 
[[Category:Math]]
 
[[Category:Math]]
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[[Category:Calendar]]
 
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[[Category:Binary]]
 

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