[uf-discuss] Using hCalendar to Create History Timelines

Jeremy Boggs jeremyboggs at gmail.com
Wed Jun 21 06:37:13 PDT 2006

Thanks for the links, Brian, and sorry for my delayed response.

Mark Pilgrim states in that microformats-dev thread that it's  
problematic when it comes to marking BCE dates.[1] Tantek agreed, but  
responded that "Alternatively, RFC2550 contains a proposal for  
representing BCE dates"[2] [3], which looks promising, but I not  
clear from the microformats-dev thread that the method is workable  
for hCalendar. Are the methods discussed in RFC2550 valid for  
hCalendar and ISO dates? I can markup a some vevents with BCE dates  
for the list, using the RFC2550 guidelines, if that would help the  
conversation. I guess that I'm not clear on the status of RFC2550  
with regard to hCalendar and the microformats community.

On a different (but related) note, and using more recent events (20th  
century), here are three examples of some timeline markup I'm working  
on. All lack specific dates for the event, and instead span an entire  
month, but each uses different methods to represent the date in the  

The first example uses both a class="dtstart" and class="dtend" to  
represent the period of June 1953. I think I've made this to specs  
with the wiki example for hCalendar, specifically with regard to the  
"end" date being July 1, 1953 to include all of June 1953:

<div class="vevent">
<span class="date"><abbr class="dtstart" title="19530601">June</abbr>  
<abbr class="dtend" title="19530701">1953</abbr></span>
<span class="summary">African-Americans in Baton-Rouge, Louisiana  
boycott segregated city buses.</span>

The second example uses only a class="dtstart" with a title value of  
"19540501" to represent the period of May 1954. The abbreviation tag  
wrap around the entire date, "May 1954." Jeremy Keith's markup of the  
15th-century Renaissance is somewhat similar to this[4]:

<div class="vevent">
<abbr class="dtstart" title="19540501">May 1954</abbr>
<span class="summary">Brown v. Board of Education of Topeka, Kansas.</ 

I'm not a fan of the previous method, simply because it uses a  
specific DAY (May 1, 1954) in the title attribute to represent the  
entire month. A third method, similar to the second, would omit a  
specific day and use only the year and month numbers in the title  
attribute, thus referencing the entire month:

<div class="vevent" id="niagara-movement">
<abbr class="dtstart" title="190905">May 1909</abbr>
<span class="summary">Niagara Movement convenes (later becomes the  
<abbr title="National Association for the Advancement of Colored  

The second example isn't great because I can add specific dates for  
the Brown v. Board trial, but the first is more problematic because  
there aren't specific begin and end dates for the event in question.  
I'm cautious about the third example because I haven't found any  
hCalendar examples that use only the year and month (are there any?).  
But, from my novice perspective, this solution seems to make the most  
sense, and is most inline with the ISO Date formats.[5]  Barring  
these caveats, which is the better method? Or are there better methods?


[1] http://microformats.org/discuss/mail/microformats-dev/2005- 
[2] http://microformats.org/discuss/mail/microformats-dev/2005- 
[3] http://www.ietf.org/rfc/rfc2550.txt   (section 3.5)
[4] http://adactio.com/articles/1132/
[5] http://www.w3.org/TR/NOTE-datetime ; http://www.ietf.org/rfc/ 
rfc3339.txt ; http://en.wikipedia.org/wiki/ISO_8601; http:// 

On Jun 16, 2006, at 10:24 AM, brian suda wrote:

> We discussed briefly the issues with ISO Dates on the Dev  List
> http://microformats.org/discuss/mail/microformats-dev/2005-December/ 
> 000045.html
> Recently, at reboot 8, which was all about the 14th century  
> renaissance,
> there has been use of vevents to describe events that took place
> hundreds of years ago[1,2].
> Because hCalendar uses ISO Dates we are limited. We can't switch  
> easily
> between gregorian and julian, as well as describe BCE dates, or  
> circa 1492.
> -brian
> [1] - http://adactio.com/articles/1132/
> [2] - http://adactio.com/journal/1141/

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