The "Aggregation Methods" screen registers and edits aggregation methods. An aggregation method allocates days to a time range in summaries. An example: - Today: today. - Last week: 1 till 7 days ago. - Last month: 1 till 30 days ago. - And so on. The entry fields are: - "Code": The code that refers to the aggregation method. - "Description": The description of the aggregation method. - "#Units": The number of units to aggregate. - "Unit of Time": The time unit over which the aggregation takes place. - "Label Expression": A SQL expression that calculates the first day in the period. All variables of the type `:start_date` are replaced by the first day in the period. The values are summed for all times after the previous period specification. An example follows after this list. For example, successive period specifications cover these days: - 2 days: day 0 till 2. - 7 days: day 2 till 7. - 1 month: day 7 till the end of the month that contains day 7.