Forecast function doesn't return good data

Paul8585 

More specifically, attach an Excel file with one or more examples.

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There are many reason why FORECAST not return "good data".

First and foremost, because your actual data does not fit a linear treadline closely.

Second, because you are using a different "flavor" of the (new) family of FORECAST functions, not FORECAST per se (without qualifier).

Finally, because you are misusing the FORECAST function.  We cannot know one way or the other unless and until you show us your formula and data -- again, preferably in an Excel file that we can download.