Hi Xia,
Currently there is no support to define different dayWorkingTime for special days in Gantt. Currently, we are working on the implementation of pure JavaScript based Gantt.
We are considering this as a feature request in pure JavaScript based Gantt(EJ2 Gantt). Hence we logged a feature report for this. You can track its status from below feedback link.
This feature will be implemented and included in any of our upcoming releases. Please cast your vote to make it count. We will prioritize the features for every release based on demands.
Regards,
Gurunathan