HTML: letter T in the time format - what for?

Question

The document http://www.w3.org/TR/NOTE-datetime

says a lot about Date and Time formats:

Examples

1994-11-05T08:15:30-05:00 corresponds to November 5, 1994, 8:15:30 am, US Eastern Standard Time.

1994-11-05T13:15:30Z corresponds to the same instant.

Complete date plus hours, minutes, seconds and a decimal fraction of a second YYYY-MM-DDThh:mm:ss.sTZD (eg 1997-07-16T19:20:30.45+01:00)

where:

 YYYY = four-digit year
 MM   = two-digit month (01=January, etc.)
 DD   = two-digit day of month (01 through 31)
 hh   = two digits of hour (00 through 23) (am/pm NOT allowed)
 mm   = two digits of minute (00 through 59)
 ss   = two digits of second (00 through 59)
 s    = one or more digits representing a decimal fraction of a second
 TZD  = time zone designator (Z or +hh:mm or -hh:mm)

But, what is T in 1994-11-05T08:15:30 for?

Answer 1

From the second paragraph of the Format section:

Note that the "T" appears literally in the string, to indicate the beginning of the time element, as specified in ISO 8601.