The Timesum formula works, as I'm getting the expected result.
Can I ask why using timesum is discouraged if the module is dimensioned by time?
I can change the time scale from "Month" to "Not Applicable". My question is if I have a bunch of employees that all have a different start month, (thus Hire Date - 1, Hire Date - 2) would all have different results, if switching the time dimension would cause an issue (Besides creating a subsidary view of those line items)
Sure, because TimeSum was designed to be used when the TimeScale was not define. It is better and more efficient to use previous, Offset, or a lookup from a SYS Time module. Take a look at Anapedia for TimeSum and you will see the following: