I am struggling with date/time calculation in VBA.

1. Can I add/subtract dates as in the next example:

Dim vStart As Date, vEnd As Date, vHours As Date

dim vHours1 as integer

vStart="20:00"

vEnd = "23:00"

vHours=vEnd-vStart

vHours gives me "03:00:00" which is correct to me. Is is simple to use, write and understand.

So why should I use vHours1 = DateDiff("n", vStart, vEnd)?

vHours1=180 (minutes) which also correct

2.

Dim vStart As Date, vEnd As Date, vHours As Date

dim vHours1 as integer

dim var1 as double, var2 as double, var3 as double

vStart="01:00"

vEnd="01:00"

vHours=vStart-vEnd

var1 = vstart

var2=vend

var3=var2-var1

vHours gives me "00:00"

in fact it is not (sometimes, not all the time !!!!)

var1=4,1666667E-02

var2=4,1666667E-02

var3=2,081668171E-17 (sometimes var3=0 !!)

So var1 <> var2 and so vStart<>vEnd !!!!!

This means that if I compare vStart and vEnd as in

if vStart=Vend then ......

sometimes they are equal and sometimes they are not

Question is :

How should I should compare times

if vStart=Vend then ......

if vStart>Vend then ......

etc.

Thanks for your help.