COMMENT(!MOD!zsh/sched
A builtin that provides a timed execution facility within the shell.
!MOD!)
The tt(zsh/sched) module makes available one builtin command:

startitem()
findex(sched)
cindex(timed execution)
cindex(execution, timed)
xitem(tt(sched) [tt(-o)] [tt(PLUS())]var(hh)tt(:)var(mm)[:var(ss)] var(command) ...)
xitem(tt(sched) [tt(-o)] [tt(PLUS())]var(seconds) var(command) ...)
item(tt(sched) [ tt(-)var(item) ])(
Make an entry in the scheduled list of commands to execute.
The time may be specified in either absolute or relative time,
and either as hours, minutes and (optionally) seconds separated by a
colon, or seconds alone.
An absolute number of seconds indicates the time since the epoch
(1970/01/01 00:00); this is useful in combination with the features in
the tt(zsh/datetime) module, see
ifzman(the zsh/datetime module entry in zmanref(zshmodules))\
ifnzman(noderef(The zsh/datetime Module))\
.

With no arguments, prints the list of scheduled commands.  If the
scheduled command has the tt(-o) flag set, this is shown at the
start of the command.

With the argument `tt(-)var(item)', removes the given item
from the list.  The numbering of the list is continuous and entries are
in time order, so the numbering can change when entries are added or
deleted.

Commands are executed either immediately before a prompt, or while
the shell's line editor is waiting for input.  In the latter case
it is useful to be able to produce output that does not interfere
with the line being edited.  Providing the option tt(-o) causes
the shell to clear the command line before the event and redraw it
afterwards.  This should be used with any scheduled event that produces
visible output to the terminal; it is not needed, for example, with
output that updates a terminal emulator's title bar.
)
enditem()