[O] est+ and time units

[Malcolm Matalka]

When you use est+, what units are the ranges in?  For example, I did
1d-2d and then another which was 40:00 and got a very different result
than doing 5d instead of 40:00.  I also tried with use 40h-40h and 5d-5d
and 40:00-40:00.  Are ranges unit-less and I just have to be careful to
always use the same unit?