Sure you are right on the class
and there is a BADI infact
HRESS_CATS_CAL_DISPLAY_IMPL, Please read more on SPRO and help docs
*&--------------------------------------------------------------------* *& Object METH CL_HRESS_CATS_CAL_DISPLAY *& IF_HRESS_CATS_CAL_DISPLAY~UPDATE_CAL_DISPLAY *--------------------------------------------------------------------* *-Default logic for cutoff date includes three options: *-1. Payroll Period enddate (Retrieved via a web service) *-2. End of current calendar month *-3. Custom implementation (Can be used by customers in custom BAdI Impl.) *--------------------------------------------------------------------* BAdI: Calendar Display for Recording Working Times Use This Business Add-In (BAdI) is used in Employee Self-Service (ESS) based on the Web Dynpro ABAP (PA-ESS-XX-WDA) component. YYou can use this BAdI to provide the time recording cutoff date information in the Calendar Summary, in addition to the completion status and incomplete days. This BAdI uses the Method to update/change calendar display (UPDATE_CAL_DISPLAY) method. Requirements As system administrator, you have done the following to enable HR-Enabled CATS to use the payroll period end date as the time recording cutoff date: •Allowed web services to connect to, and retrieve data from, the HR system by maintaining the settings in Customizing under Cross-Application Components -> Processes and Tools for Enterprise Applications -> Enterprise Services -> General Settings for Enterprise Services -> Manage and Test Enterprise Services. ◦Configured the consumer service PayrollProcessERPBasicDataQueriedEmployeeByEmployeeQueryResponse_In ◦Configured the consumer proxy CO_CATSPAYROLL_PROCESS_ERPBASI •Set the logical port created for this consumer proxy as the default port. Standard Settings For more information about the standard settings (filters, single, or multiple uses), see the Enh. Spot Element Definitions tab in the BAdI Builder (transaction SE18). BAdI Implementations Depending upon the data entry profile Customizing, the default implementation shows either the end date of the current payroll period or the last day of the current calendar month as the due date for time recording. Activities For information about implementing BAdIs as part of the Enhancement Concept, see SAP Library for SAP NetWeaver under BAdIs - Embedding in the Enhancement Framework.