The horizontal cursors may be used to measure the duration of a section of a waveform as shown below.
The values of the two cursor positions are displayed at the bottom left of the plot area, along with the difference between them. The difference has a blue background and the units may be changed by clicking on it. If the display shows time units and the user clicks on it, the units will change to frequency units.
Similarly, if the display shows frequency units a click on the blue area will change the units to time units.