Header and Footer on slides
To add or change a header and/or footer in your presentation, follow next steps:
1. On the Insert tab, in the Text group, click Header and Footer or Date and Time or Slide Number:

2. On the Slide tab, select the check boxes for each of the three elements that you want to use:

You can set Date and Time either to Update Automatically or to Fixed:
- Update Automatically pulls the current date from the computer's clock and formats it in whatever format you choose from the drop-down list. You can also select a language and a Calendar Type (although this is probably not an issue unless you are presenting in some other country than the one for which your version of PowerPoint was developed).
- Fixed prints whatever you enter in the Fixed text box. When Fixed is enabled, it defaults to today's date in the mm/dd/yyyy format.