One may set
org-deadline-warning-days to have
DEADLINE items show up a default number of days before the deadline in the agenda, or one may do it on a case-by-case basis by adding, e.g.,
-3d to the
Now, using the same warning notation
-3d on a
SCHEDULED item produces the reverse effect: the item is not added but skipped from the Agenda view for that number of days.
From the Org-mode manual:
If you want to _delay_ the display of this task in the agenda, use `SCHEDULED: <2004-12-25 Sat -2d>': the task is still scheduled on the 25th but will appear two days later. In case the task contains a repeater, the delay is considered to affect all occurrences; if you want the delay to only affect the first scheduled occurrence of the task, use `--2d' instead. See `org-scheduled-delay-days' and `org-agenda-skip-scheduled-delay-if-deadline' for details on how to control this globally or per agenda.
What can this be useful for?
My understanding is if you want to start working on an item and you schedule it for a specific date, you want to start seeing the item in the agenda at least on the scheduled day, and may be even earlier, but definitely not later.
Am I missing something?