  The Geostationary Orbital Environmental Satellites (GOES) Soft X-ray (SXR)
sensors have provided data relating to, inter alia, the time, intensity and
duration of solar flares since the 1970s. The GOES SXR Flare List has become
the standard reference catalogue for solar flares and is widely used in solar
physics research and space weather. We report here that in the current version
of the list there are significant differences between the mean duration of
flares which occurred before May 1997 and the mean duration of flares
thereafter. Our analysis shows that the reported flare timings for the pre-May
1997 data were not based on the same criteria as is currently the case.
  This finding has serious implications for all those who used flare duration
(or fluence, which depends on the chosen start and end times) as part of their
analysis of pre-May 1997 solar events, or statistical analyses of large samples
of flares, e.g. as part of the assessment of a Solar Energetic Particle
forecasting algorithm.
