In short, if you work with diodes, you need this standard.

This is the most famous parameter. It is the time interval between the instant the diode current passes through zero (when switching from forward conduction to reverse blocking) and the instant the reverse current decays to a specified percentage of its peak reverse current (typically 25% or 10%, depending on the device).

The standard specifies a chuck temperature tolerance (e.g., 25°C ± 2°C or 125°C ± 5°C). Testing an oxide at room temperature versus 125°C changes the breakdown voltage by nearly 15%.