Difference between apparent electron release time (TSA) and the time derivative maximum of X-ray intensity as a function of the connection angle (the longitudinal distance of the flare from the Earth-connected Parker spiral footpoint) for the catalogued events, with outlying data points (see text) omitted. The red symbols represent solar cycle 23 (1996–2008) events, and the blue symbols represent solar cycle 24 (2009–2016) events; the fit lines coincide nearly perfectly in this graphic. The lower equations refer to the linear fit for solar cycle 23 events, the upper ones to the linear fit for solar cycle 24 events.