In an 11.8 SBM report filter, "Submit Date <= 8/31/23" not yield items whose Submit Date is 8/31/23, that ARE included if the condition is "Submit Date = 8/31/23".  In both cases, after the condition is created, the condition time appears as midnight (12:00:00 am).  

In the case then of "Submit Date <= [8/31/23] 12:00:00 am", it makes sense to me that items submitted 8/31/23 are not included, since the limit is expressed as midnight.

However, for "Submit Date = 8/31/23 12:00:00 am", since midnight is not a time range, I infer that the "12:00:00 am" is meaningless.

Obviously, for hard-coded dates, using "Submit Date < 10/1/23" is the solution, preferable to adding an appropriate time in "Submit Date = 8/31/23".

Whatever the case, it seems to me that since entering <= [date] seems to make sense for including [date], maybe there could be a popup warning, or the time should instantly fill in as a reminder.

The Date/Time Keywords are inclusive, so that's good.