AutoDateTime

Even though an interactive PowerPoint presentation is bound to draw your audience's attention, paying attention to the little touches can make you look more professional and determined. While it is true that the program offers you several options in this sense, sometimes you might need more than the default features to stand out.
AutoDateTime is a Microsoft PowerPoint add-in that enables you to change the time/date format so that it displays the time elapsed from the beginning of the slideshow.

Easy setup and seamless UI integration

The installation is as simple as it gets and you should not experience any issues. You can access the add-in from the Insert tab from PowerPoint's toolbar. In case you are using the 2003 or earlier version, then you can find the extension in the Format menu. It goes without saying that the utility borrows the looks of the PowerPoint version you are using.
It is necessary to mention that you need to access the add-in and enable it before you can alter the time display. Since it does not include a menu of is own, it might create some confusion for some users.

Comes with various time/date customization options

Granted, some users can argue that you can already customize date display in PowerPoint by changing the font, style, size, location, color, so on and so forth.
Then again, the idea behind the add-in is to provide you with an extra option to display time and date, one that can incorporate the time elapsed from the beginning of the slide. Moreover, you can specify exactly what you want to show, meaning AM/PM, weekdays, months as well as years in either standard or short format and the hours in military format.
The feature can come in handy in various situations, such as when you are holding a seminary and are trying to explain how a particular problem can get solved.

A professional option for your presentations

In the eventuality that you are trying to put an emphasize on efficiency and time during your presentations, then perhaps AutoDateTime might be the extension to help you achieve this goal.