It is important to understand the difference between forecast shots and forecast history.
Forecast shots are historical forecast attempts, i.e, in August 2020 the item was forecasted to sell 756 units in July 2021. Each data point on the image below is a forecast shot.
Forecast history is the average forecast attempt (forecast shot) for a given month. It is calculated as the average shot (forecast attempt) over the cover forward period (LT + SS + RC). The cover forward period is the duration over which the forecast impacts the immediate order recommendation and is a good basis for assessing impact and performance.
The forecast history for July 2021 in the image below is the average of the green values in the column.
Please refer to the article How do I read the Forecast history table? for a more detailed explanation.
When do forecast shots get regenerated?
Forecast shots are regenerated for all items when "Regenerate forecasts" is selected from the Data Refresh page or from Settings > Configuration > Forecast.
Otherwise, shots are only recalculated for the following:
Newly downloaded items
Items with a changed supersession structure
Items with a classification that changed from non-stocked/obsolete to stocked
Items with age <= 4 (only if "Forecast Young items daily" is enabled)
When entering a new month, the previous month's forecasts are preserved as a new shot so long as the above scenarios do not trigger a recalculation.
When does forecast history get regenerated?
Similar to shots, forecast history is regenerated for all items when "Regenerate forecasts" is selected from the Data Refresh page or from Settings > Configuration > Forecast.
In addition, forecast history is also regenerated when entering a new month.
Remember that the underlying forecast shots will generally be unchanged, subject to the exceptions above. However, the cover forward period can change, which might result in using more or less forecast attempts when computing the average.
During a regular daily batch, history is recomputed for the following:
Newly downloaded items
Items with a changed supersession structure
Items with a classification that changed from non-stocked/obsolete to stocked
Items with age = 1
Forecast history is computed using the final forecast from the forecast shots, meaning that it will incorporate any frozen forecasts as well as unfrozen changes applied via the macro adjustment feature.