Question about year 0000 between JDK and JodaTime about joda-time

[jodastephen]

Three issues

1. Joda-Time has extended time-zone information such that dates in the far past like this are at a local offset from GMT.

2. Joda-Time uses the ISO calendar system, which differs from the GregorianCalendar class before 1582. In 1582 you would see 10 days difference (due to leap year pattern differences). However, once you are back as far as year zero, there is only 2 days difference.

3. Year zero doesn't exist in GregorianCalendar, but it does inISOChronology`. As such, when you create the year zero date, you are actually creating 1BC, hence the 0001 in the format. Joda does have a year zero, so displays it as such.

Finally, bear in mind that the SimpleDateFormat uses the default time-zone and the default 1582 cutover date unless you tell it otherwise.