Time
We frequently describe events in our daily communications. As humans, we can easily interpret statements such as 'would you like to hang out tonight?' or 'my birthday is 1/7/81.' These statements are ambiguous on a couple of levels. First, 'today' is constantly changing. An event taking place 'today' quickly becomes yesterday's news. The second example even gives us humans difficulty. Is the date July 1st, 1981 or January 7th 1981?
HTML5 provides us with a tag to explicitly convey dates and times. The tag, as with most HTML tags, is appropriately named:
- <time>
The <time> tag has an attribute called datetime**. The datetime attribute takes a specifically formatted string:
YYYY-MM-DDTHH:MMTZO
YYYY = four digit year
MM = two digit month, zero padded if necessary
DD = two digit day, zero padded if necessary
T = time separator, do not change
HH = hour, 24 hour (e.g. 13 = 1PM), zero padded if necessary
MM = minute, two digits
TZO = timezone offset, +/- 23:59 (typically whole hour offset)
An example of a specific event would be August, 21st, 1999 355PM GMT -8:
<time datetime="1999-08-21T15:55-08">
The <time> tag also has a boolean attribute called pubdate. When pubdate is present in a <time> tag, the event is taken to be the publishing date of the parent element (such as an <article>.)
The time format adheres to a convention, designated by the International Standards Organization, called ISO 8601:
The standard organizes the data so the largest temporal term (the year) appears first in the data string and progresses to the smallest term (the second). It also provides for a standardized method of communicating time-based information across time zones by attaching an offset to Coordinated Universal Time (UTC).
Discussion Questions
Please answer the following questions in the discussion section for this task.
- What do you see as beneficial about HTML5 adopting the ISO 8601 date format? I.e. How is having the date format starting with year beneficial?
- How do you normally write dates? What punctuation do you use between date elements?
- What are some other classification or designation systems where the largest components precede the smaller ones?
Extra Credit
The datetime attribute assumes that dates are relative to the Gregorian calendar (Inter gravissimas). Describe one or more alternative calendars including a brief history, merits, as well as shortcomings of the each calendar.