While performing a critical path analysis, I noticed negative slack for both ed days and work days. I tried to filter on the negative ed days in the drop-down pick list for total slack which resulted in a blank column. This leads me to wonder how ed days are calculated in slack, if at all and why wouldn’t project show me tasks with negative ed days. I would appreciate any information on this subject. Thanks!
First, perhaps you are having a problem with the syntax of your filter specification. I have no trouble isolating tasks with negative elapsed Total Slack using a custom filter comprising two conditions: 1) Total Slack is less than 0; AND 2) Total Slack contains e. In the first condition, Project will append the symbol for the default duration unit (the letter d typically in English). The second condition requires no quotes around the letter “e”. An identical result can be obtained using either a custom filter or a custom autofilter.
If a task has a duration that is entered in elapsed days, then its Total Slack (and all other duration fields) will be displayed in the same units, elapsed days. Ultimately, they are stored in plain old “minutes” (just like all other durations in Project), with a separate field holding the “elapsed day” attribute. Thus, if Total Slack for Task A is “1d”, and Total Slack for Task B is “1ed”, the stored numerical values for Total Slack are 480 (1d x 8h x 60min) and 1440 (1d x 24h x 60min) respectively. (You can easily see these values using a simple “=[Total Slack]” formula in a custom number field.) The internal calculations all take proper account of the other attributes to make the numbers work. One hitch: the advanced calculation option “Tasks are critical if slack is less than or equal to __ days” makes a conversion to minutes using the project’s sole “Hours per day” schedule option, which is typically 8. As a result, the threshold needs to be set at 3 days to catch (and mark as “Critical”) a task with TS = 1 eday.
Good luck, tom