Any of the elements of an ISO 8601 time element can have decimal fractions added to any number of digits. But only the lowest element (according to Wikipedia be

Any of the elements of an ISO 8601 time element can have decimal fractions added to any number of digits. But only the lowest element (according to Wikipedia because I don't have the actual standard in front of me). But you can definitely have a timestamp of 2020-07-23T12:37:55.758145Z The standard acommodates timezones as offsets from UTC, because it's a representation of a timestamp, not a local time at a particular geographical location. So things like daylight savings time periods are not relevant.