You can accomplish this by going to Settings > Time & Expenses > Time Entry and setting the 'Time entry should not be saved/deleted if older/newer than...' rule for your company. Adjust as necessary for your pay period and click Save when you are done.
If you do not want this applied to all your employees, you can change the settings to allow specific employees to bypass this setting. Open the Security Permissions screen from Settings > Access & Permissions. Select the employee you want to allow to bypass, such as a project manager, and change the permission for that person under the Time Entry section. Enable the option: Allow adjust date beyond settings restriction. Click Save and you're all set!