the fireworks should be at about 8 pm. since singapore idol starts at 8.15.
*edit. Quote from NDP website.
Fireworks and Flypast Timings
Members of the public might be interested to know that the flypast display will be from approximately 7.10pm to 7.40pm. There will be a small fireworks display from approximately 7.25pm to 8.20pm. Motorists are advised not to stop on Mountbatten Road, Nicoll Highway & East Coast Parkway (ECP) to view the fireworks display so as to avoid potential traffic jams/accidents.