help me in creating Gantt chart

I am using this video tutorial to create a Gantt chart

http://www.youtube.com/watch?v=CW_wGSFavTc


My data is something like this

Task StartDateTime Cap Duration(Minutes)
task1 4/20/09 6:00 AM 4
task2 4/20/09 9:00 AM 20
task3 4/20/09 12:00 AM 8
task4 4/20/09 12:00 AM 1
task5 4/20/09 12:00 AM 46
task6 4/20/09 12:00 AM 10
task7 4/20/09 12:00 AM 0
task8 4/20/09 12:00 AM 0
task9 4/20/09 12:00 AM 2
task10 4/20/09 12:00 AM 2
task11 4/20/09 12:00 AM 9
task12 4/20/09 12:00 AM 1
task13 4/21/09 12:00 AM 1
task14 4/20/09 12:00 AM 21

I am facing problem once I set the min and max value for the horizontal axis as described in the tutorial. The horizontal bar graph are not displayed correctly. For e.g. Task1 starts correctly at 4/20/09 6 am but extends all the way to 4/23rd while duration is just 4 minutes. I think I have got something wrong while mapping the duration in minutes to horizontal axis.Can someone help. I have attached the graph as gif file.