Specific time duration based on day of week

Content

HI all

Need some help with time/date, I am trying to creating a report with the following set up

                                                                        Shift 1  Shift 2 Shift 3

Incidents Closed

Shift Times

Shift 1  6pm (previous day) to 6am (today)

Shift 2  6am to 12noon

Shift 3  12noon to 6pm

Incidents Closed Totals for the shifts would be

Shift 1  6pm (previous day) to 6am (today)

Shift 2  6pm (previous day) to 12noon

Shift 3  6pm (previous day) to 6pm

The issue i am having is, On my filter I have “date_add(date_add(sysdate(), -1, DAYS, 1), 6, HOURS, 1)”

This does not specified a specific time to start or stop by day. What am looking for is a filter on time, start back 1 day 6pm to current day 6pm.