When we assign ETC for a resource, it doesn't seem to disperse across the entire Time Scale (TSV) timeline. For example, a resource is assigned to a task from 10/5/20 to 12/31/21 but the ETC seems to only start at 12/28/20 (4 weeks prior to the current week)
This is due to a limitation in how far back time scale period data is able to be displayed. Out of the box you can only see 2 weeks in the past, and with an extension, you can see 4 weeks in the past.
If you see a message in yellow at the top of the task page saying "‘The time periods requested do not exist", that is one other indicator that one or more time scale periods shown is outside the limit.
Release : All Supported
Component : CA PPM PROJECT MANAGEMENT
It's not possible to update the Time scale in Classic Clarity to show data prior to the limits. See the following KB for detailed information for how much in the future and how far back in the past data is able to be displayed: "The time periods requested do not exist" Warning when moving to future or past periods on a TSV field.
Note: You can use the Modern User Experience (UX) to see the entire duration of the date range for ETC using the per-period metrics on the STAFF (as of 15.9.1) or ASSIGNMENTS grids (as of earlier versions)