• W H Cordell, M L Olinger, P A Kozak, and A W Nyhuis.
• Emergency Medicine and Trauma Center, Methodist Hospital of Indiana, Indianapolis.
• Ann Emerg Med. 1994 May 1; 23 (5): 1032-6.

Study ObjectiveTo evaluate the difference among time sources in an emergency medical system.DesignProspective; comparison to a criterion standard.SettingFive emergency departments and three emergency medical services systems in Indianapolis, Indiana.InterventionsCoordinated Universal Time (UTC), generated by the atomic clock in Boulder, Colorado, and broadcast by the US Commerce Department's National Institute of Standards and Technology, was used as the time standard. The investigators, on a single day, made unannounced visits to the five EDs and the ambulances and fire stations in the three emergency medical services systems. The times displayed on all time sources at each location were recorded. The accuracy to the second of each time source compared to UTC was calculated.ResultsThree time sources were excluded (two defibrillator clocks and one ED wall clock that varied more than three hours from UTC). Of the 152 time sources, 72 had analog displays, 74 digital, three both, and three other. The average absolute difference from UTC was 1 minute 45 seconds (SEM, 9 seconds) with a range of 12 minutes 34 seconds slow to 7 minutes 7 seconds fast. Thus, two timepieces could have varied by as much as 19 minutes 41 seconds. Compared to UTC, 47 timepieces (31%) were slow, 100 (66%) were fast, and five (3%) were accurate to the second. Fifty-five percent of the time sources varied one minute or more from UTC.ConclusionTime sources in this health care system varied considerably. Time recording in medicine could be made more precise by synchronizing medical clocks to UTC, using computers to automatically "time stamp" data entries and using only digital time sources with second displays.

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