Calculating early and late arrival for performance

I am trying to calculate shipping performance- Im getting stuck in several areas and I hope i can get some help!

I have an Estimated Ship Date, an Appt Date, and an Actual Ship date.

Im measuring warehouse performance, so in most cases shipments leave same day. But in others, they may leave a few days early or late.

The problem that i am having is the correct output. I want to show the Values in DD:HH:MM, but the syntax for DateDiff doesn't give me an accurate day to use:

For Example, a shipment was supposed to leave on 6/3/2019 @ at 8 am, but didnt leave the warehouse until 7/22/2019 @ 6:30 AM. In this case, DateDiff calcs 49 days, when really its 48 days 22 hours and 30 minutes late. Here is an example of some of the syntax i am using:

What I have tried:

create table #test (
  EstimatedShipDate datetime,
  AppointmentShipDate datetime,
  ActualShipDate datetime
  );

insert into #test values ('2019-07-01 11:00', '2019-07-01 11:00','2019-06-30 10:30');
insert into #test values ('2019-07-08 13:45', null,'2019-07-01 22:00');
insert into #test values ('2019-07-09 15:00', null,'2019-07-10 15:00');
insert into #test values ('2019-07-03 15:00', null,'2019-07-04 15:00');
insert into #test values ('2019-07-08 15:00', null,'2019-07-08 15:00');
insert into #test values ('2019-07-08 15:00', null,'2019-07-08 22:00');
insert into #test values ('2019-07-03 08:00', null,'2019-07-04 15:00');
insert into #test values ('2019-07-03 08:00', null,'2019-07-03 06:30');
insert into #test values ('2019-06-03 08:00', null,'2019-07-22 06:30');
--insert into test values (3, '2012-01-02 12:00');

Select 
EstimatedShipDate,
AppointmentShipDate,
ActualShipDate,


DATEDIFF(DAY,ISNULL(CAST(AppointmentShipDate as DateTime),CAST(EstimatedShipDate as DateTime)), CAST(ActualShipDate as DateTime)) as Days,

convert(varchar, CAST(ActualShipDate as DateTime)-ISNULL(CAST(AppointmentShipDate as DateTime),CAST(EstimatedShipDate as DateTime)),108) as DateSubtract_Convert,

convert(varchar,ISNULL(CAST(AppointmentShipDate as DateTime),CAST(EstimatedShipDate as DateTime)-CAST(ActualShipDate as DateTime) ),108) as DateSubtract_ConvertEarly
from #TEST

Using the example above output looks like:

EstimatedShipDate	2019-06-03 08:00:00.000
AppointmentShipDate	null
ActualShipDate	2019-07-22 06:30:00.000
Days	49	
DateSubtract_Convert	22:30:00
DateSubtract_ConvertEarly	01:30:00

Any advice is greatly appreciated!

Tags: SQL, DateTime, Syntax