The date field you probably want to use is "Work Entry Day" rather than "Work Entry Created On." Unless I'm mistaken, the Work Entry Day is the calendar day the Task Hours are reported against the task, where Work Entry Created On is the day the work entry was (obviously) created.
This way, if a Work Entry record for work done on Wednesday the 8th was created at Friday the 10th, the dates should reflect accordingly. This should break down the work entries by the day the hours were worked rather than the day the work was actually entered in the system.