item "Early Warning..." setting has no effect

[Seth Teller]

Using ical v1.7, create an "item" in the lower-left pane for some future date, say a week from now.
That generates this text in ~/.calendar:

Note [
Length [30]
Uid [scooby-doo_1e808d02_4118_4eda]
Owner [seth]
Text [9 [TEST ITEM]]
Remind [2]
Hilite [always]
Dates [Single 13/12/2012 End
]
]

Next, highlight the item and select Item->Early Warning, and set the slider to (say) 14 days. Now the text reads:

Note [
Length [30]
Uid [scooby-doo_1e808d02_4118_4eda]
Owner [seth]
Text [9 [TEST ITEM]]
Remind [14]
Hilite [always]
Dates [Single 13/12/2012 End
]
]

Since the item is a week in the future, and we've requested 14 days of early warning, that item should be
displayed in today's reminders. But it is not. The "early warning" attribute, though it is getting written to
the .calendar file correctly, seems to have no effect.