ISODateTimeFormat: make millis optional in dateTime format by default

When using joda-time to parse xsd:dateTime values, the developer is forced to choose statically whether their date is a dateTime or as dateTimeNoMillis.

However, it is not uncommon for XML parsers, transformers and XPath engines to optimise xsd:dateTime values with a ,000 fractional part, and completely strip away the milliseconds section.

Try this in Saxon 9.x (XPath 2.0) – probably the most popular XSLT 2.0 parser out there:

'2006-12-28T15:42:04.000+01:00' cast as xs:dateTime

returns

2006-12-28T15:42:04+01:00

Obviously one can create a custom parser with an optional millis part, but this is not intuitive, and certainly not a nice OOTB experience with Joda.

Therefore I propose to modify the dateTime() method to return a formatter that considers the millisecond part as optional OOTB. It doesn’t harm anybody and contributes positively to the usability of Joda.

[jodastephen]

Changing the meaning of these formats at this point in Joda-Time’s life would essentially be backwards incompatible. The parser is intended for handling variable length input, whereas the dateTime() and dateTimeNoMillis() handle output and parsing of fixed length formats.

[mrjink]

The returned formatter prints and parse should be The returned formatter prints and parses. See {@link #dateTimeParser()} for a more flexible parse should be See {@link #dateTimeParser()} for a more flexible parser. This same text occurs 26 and 13 times, respectively.