We need to change the formatting, and with 3 decimal places, we only need to skip 1 millisecond's activity
Dim strStartDate As String
Dim strEndDate As String
strStartDate = Format(Now - 1, "yyyy-mm-dd 6:00:00.001")
strEndDate = Format(Now - 1, "yyyy-mm-dd 6:00:00.000")
Then use the variables in your code instead of the Format function
The truth is, Microsoft stores dates as 15 decimal place numbers, so even if you did use 6AM for both Times, the odds are greatly against reporting the same activity twice.
You might also try
Dim dteStartDate As Date
Dim dteEndDate As Date
dteStartDate = DateAdd("d", -.75, Date)
dteEndDate = DateAdd("d", .25, Date)
If you use Now to return a Date, you also get the 15 decimal place time portion, but Date only returns the Integer portion.