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Hello, I have recently been estimating simple linear regressions and comparing the results with another program (eviews) has given me a variation in the value of the constant. According to what I have looked for, in the eviews program it is estimated from time zero instead of starting at one time would you like to know why this happens? On the other hand, from the same series I have estimated the trend, and I would like to know the criterion for estimating it, because I get the same result. I would also like to know if there is a way that when I add trend line in a graph, it estimates me from zero and not from one. I would appreciate more technical and theoretical information about how this is done. Thank you.