They're still likely to be accurate to within 90 seconds or so i'm presuming though?
This is what James C. Bowles, the man in charge of the Dallas Police dispatchers, told the HSCA;
A master clock on the telephone room wall was connected to the City Hall system. This clock reported "official" time. Within the dispatcher's office there were numerous other time giving and time recording devices, both in the telephone room and in the radio room. Telephone operators and radio operators were furnished "Simplex" clocks. Because the hands often worked loose, they indicated the incorrect time. However, their purpose was to stamp the time, day and date on incoming calls. While they were reliable at this, they were not synchronized as stated in the Committee report. Therefore, it was not uncommon for the time stamped on calls to be a minute to two ahead or behind the "official" time shown on the master clock. Accordingly, at "exactly" 10:10, various clocks could be stamping from 10:08 to 10:12, for example. When clocks were as much as a minute or so out of synchronization it was normal procedure to make the needed adjustments. During busy periods this was not readily done.
In addition to the times stamped on calls by telephone operators, the radio operators stamped the "time" as calls were dispatched, and the "time" that officers completed an assignment and returned to service. Radio operators were also furnished with 12-hour digital clocks to facilitate their time references when they were not using call sheets containing stamped time. These digital clocks were not synchronized with any time standard. Therefore, the time "actual" and time "broadcast" could easily be a minute or so apart.
http://www.jfk-online.com/bowles1.html#setBtw, we know from their testimony that Shelley and Lovelady re-entered the TSBD about five minutes after the shots. Sgt Harkness, in his testimony, states that he sealed off the back entrance of the TSBD at around 12.36 or 12.37.
If, as you assumed earlier, Adams and Styles waited several minutes on the 4th floor, before coming down the stairs and seeing Shelley and Lovelady (who were not there until approx 12.35), have you already figured out how Adams and Styles could leave the building, run to the railway yard where a policeman turned them back, walked to the front of the building and subsequently to the main enterance, on the other side of the building, where Adams heard the radio call and then walked down Houston street to the loading dock where she re-entered the TSBD prior to the building being sealed off by Sgt Harkness at around 12.36 or 12.37?
