Invalid Date in function AddToDate - A common T&L error

A common error you encounter in a fresh environment while accessing T&L pages is shown below:


This error occurs due to the T&L Dates table and T&L Calendar tables not being built for the period in question.
Use the Build Time Period Calendar process available in the following navigation to build calendars for the concerned date:
Setup HRMS --> Product Releated --> Time and Labor --> Periods --> Build Time Period Calendar. After the calendars are built, you can check the View Time Calendar link to see the dates for which the calendars have been created.

Also ensure that the Load Dates process has been run. For this, go to Setup HRMS --> Installation --> Product and Country Specific --> Time and Labor installation. Go to the second tab in the T&L installation page and click on the link called Load Dates.

These are mandatory checks while setting up T&L for a fresh environment. While we are on this topic, let me also mention that it will be required to create TimeZone offsets for the Time Administration process to run correctly.
This can be done via: Peopletools --> International --> Timezones --> Click on the button called Generate Query Offsets.

As noted in this post - add the above setups into your annual maintenance checklist for T&L. These tables will have to be updated for the product to work correctly.