-@example
-# ISO 8601 extended date and time of day format
-1972-09-24T20:02:00,000000-0500
-@end example
-
-@cindex @sc{iso} 8601 date and time of day format
-@cindex date and time of day format, @sc{iso} 8601
+In this format, the time of day should use 24-hour notation.
+Fractional seconds are allowed, with either comma or period preceding
+the fraction. ISO 8601 fractional minutes and hours are not
+supported. Typically, hosts support nanosecond timestamp resolution;
+excess precision is silently discarded.