As a result of the fix for bug #4254589, the date based add()/roll() behaviour has been documented out. However, for those based on time (milliseconds) calcuration is still not clear. e.g. roll(DAY_OF_YEAR, 30) will advance 30(days) * 24 * 60 * 60 * 1000 milliseconds, not 30 days -- this affects the result day, if there is DST switching between. Say, "4/1/99 0:0 PST" roll(DAY_OF_YEAR, 30) will result in "5/1/99 1:00 PST".

1) add() almost all fields (except ERA, YEAR, MONTH) are computed based on milliseconds.

2) roll() DAY_OF_YEAR,DAY_OF_WEEK,DAY_OF_WEEK_IN_MONTH are all computed on milliseconds base.

3) Also, add()/roll() ZONE_OFFSET, DST_OFFSET will throw IllegalArgumentException.

All these spec should be documented out.
koushi.takahashi@japan 1999-10-15