np
just make for your own text formula field or time of day formula field to bucket the ties by hour, and then group on equal values.
If you use a formula text field you will need to contrive to have them list in alpha sequence to ensure that 9:00 am is before 1;00 pm., so you may need to ad a leading space.
for example
var TimeOfDay Time = ToTimeOfDay([my date / time field]);
IF(
$Time < ToTimeOfDay("7:00 am"), " Before 7:00 am",
$Time < ToTimeOfDay("8:00 am"), " 7-8" ,
$Time < ToTimeOfDay("9:00 am"), " 8-9" ,
etc
$Time < ToTimeOfDay("1:00 pm"), " 12-1" ,
$Time < ToTimeOfDay("2:00 pm"), "1-2" ,
$Time < ToTimeOfDay("3:00 pm"), "2-3" ,
etc
)