Returns unique timestamps rounded down to the date (SQLite)

gistfile1.sql

SELECT DISTINCT (round(timestamp / 86400000.0 - 0.5) * 86400000.0) as time FROM timeline ORDER BY timestamp ASC
	--in AIR, set itemClass to Date
	--the returned dates are offset with the computer's timezone, so you need to reverse it: date.time += date.timezoneOffset * 60000;