Using PowerPoint to time your presentations?

Zainul at How-to Geek writes …

Delivering a presentation is not just about giving good slides, it is also about making sure that our presentation finishes by the time our audience wants to have their tea break—so practicing how long to speak for each slide is essential for a proper presentation.

and goes on to explain how to rehearse the timing of the presentation, even how to set up the slide show to run by itself.
Useful information for when you have a presentation that needs no flexibility. Thank you How-to Geek!