Hi Lumax,
Greetings from Syncfusion.
After reviewing your query, currently do not have support to set different dayWorkingTime for each day in Gantt functionality.
We already logged feature request for the requirement. You can track the status of the feature from the feedback link given below.
We will implement this feature and include it in any our upcoming releases. You can communicate with us or track the status of the feature using the feedback link.
Until we appreciate your patience.
Regards,
Sridharan