Have a dataset which consists of item names (rows) and monthly values of sales (columns). My task is to predict value of sales for next month and I'm trying to use regression models for that. But the situation in this case that I can train only on my existing months and predict the last one available in the dataset. How is it possible to use this trained model for doing regression for next month and is it possible or the only way to use only time series prediction models?
Regression does not apply to data that is autocorrelated i.e. time series data or spatial data. http://autobox.com/dave/regvsbox.pdf (which I authored) discusses issues/differences/opportunities/pitfalls when dealing with time series that your possible regression solutions may be ignoring.
Training and other related questions are valid questions when you are using appropriate methodology.