Recently a potential employer posted a Job on odesk, wanted a script to clear the Google Spreadsheet content daily using Google Spreadsheet PHP API. I told him about Google Apps Script, and how we can use it to achieve this as using PHP API wasn't a requirement.
Using Google Apps Script we can clear the content of the Google Spreadsheet daily or on specific time of the day.
1) Open the spreadsheet and click Tools > Script Editor.
2) Copy and Paste the following Google Apps Script
Save and give relevant name to the script.
3) Set Trigger to execute the 'clear' function at midnight
Triggers > Current Scripts Trigger > Add New
This script also adds a new menu to toolbar, Scripts > Clear
We can set different type of triggers, for more read script guide.
P.S. Tad, Enjoy!