XML date and time are in the format
'-'? yyyy '-' mm '-' dd 'T' hh ':' mm ':' ss ('.' s+)? (zzzzzz)?
were
•'-'? yyyy is a four-or-more digit optionally negative-signed numeral that represents the year; if more than four digits, leading zeros are prohibited, and '0000' is prohibited
•the remaining '-'s are separators between parts of the date portion;
•the first mm is a two-digit numeral that represents the month;
•dd is a two-digit numeral that represents the day;
•'T' is a separator indicating that time-of-day follows;
•hh is a two-digit numeral that represents the hour; '24' is permitted if the minutes and seconds represented are zero, and the dateTime value so represented is the first instant of the following day (the hour property of a dateTime object in the ·value space· cannot have a value greater than 23);
•':' is a separator between parts of the time-of-day portion;
•the second mm is a two-digit numeral that represents the minute;
•ss is a two-integer-digit numeral that represents the whole seconds;
•'.' s+ (if present) represents the fractional seconds;
•zzzzzz (if present) represents the timezone (as described below).
here are more examples
Simple Example 2009-08-31T19:30:00
More complex examples
2002-10-10T12:00:00-05:00 (noon on 10 October 2002, Central Daylight Savings Time as well as Eastern Standard Time in the U.S.) is 2002-10-10T17:00:00Z, five hours later than 2002-10-10T12:00:00Z.
see www.w3.org/TR/2004/REC-xmlschema-2-20041028/datatypes.html for more info