Indicates whether to calculate using time intervals. When this checkbox is cleared (default), all other properties on this page are unavailable and ignored during LCC calculations. If this checkbox is cleared when variables do vary by time intervals, zero is used as the value for each variable. When this checkbox is selected, other properties are made available on this page. The equation for each item in the CBS tree is run once for every selected time interval. The total cost for the top-most item in the CBS is obtained by adding together the cost calculated for each time interval. If alternatives are also selected, see Alternative and Time Interval Calculations for more information.

When selected, costs are calculated for all time intervals in the LCC Variables file.

When selected, the buttons described in Alternative and/or Time Interval Selections become available so that you can add and remove specific time intervals from those in the LCC Variables file. The Available list on the left displays the time intervals that are available for selection. The Selected list on the right displays the time intervals that have already been selected.