Trips that can be done in a day are listed here. Most destinations closer to Bangalore can be done as a half day trip. I normally like to do a early start (before 7AM). For some of the half day options, you can return home for lunch. For the day long ones, it would be best to pack picnic lunches for the locations that have no good food options. With so many places around Bangalore, you will be busy for a long time!!