Why does it even matter when?
It matters due to the currently accepted :20 second timeline attached to the Couch and Darnell Films showing DPD Officer Baker. If that :20 second time line is wrong, then Wiegman filming the JFK Limo going under the Triple Underpass is also wrong. This would challenge the length of time the JFK Limo was on Elm St and the Current Zapruder Film showing the Limo on Elm St.