nirmala,

1) In JavaScript months are indexed from 0-11 and not from 1-12. Please refer to this post.

So, December 2nd should be new Data (2014, 11, 2)

2) Issue is because the automatically calculated interval is in hours and you have set valueFormatString to show MM/DD. So for every hour it is showing same month and date. Instead you also need to set interval and intervalType property as show in this jsfiddle.

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Anjali