Calculating Time Between Time/Days In Excel - excel

Question

I am having some difficulty finding the optimal solution to a problem I am having with Excel. Right now, I have a large sheet which has time on one axis (column A is every date between 1/1/2018 to 1/1/2019), and in the sheet I have time using the h:mm:ss function in different cells on different intervals.
For example, for rows 1/1/2018 - 1/3/18, there is a starting time on 1/1/2018 (example, 8:00:00), and then an ending time on 1/3/18 (example, 16:00:00).
The time between those two dates and two times on those dates is what I am looking to calculate.
This is on a sheet with 2000+ rows, and each interval is different (some may be three days, some may be the same day). The difference between all of these is another column with location. This looks like:
Row 2) Date, Location [A], Arrival Time (8:00:00), Departure Time (blank)
Row 3) Date (the next day), Location [A] (the same as above), Arrival time (blank), Departure Time (16:00:00)
+---+----------+----------+---------+-----------+
| | A | B | C | D |
+---+----------+----------+---------+-----------+
| 1 | Date | Location | Arrival | Departure |
| 2 | 1/1/2018 | A | 8:00 | |
| 3 | 1/2/2018 | A | | 16:00 |
| 4 | 1/3/2018 | B | 8:00 | 16:00 |
| 5 | 1/4/2018 | C | 5:00 | 13:00 |
| 6 | 1/5/2018 | C | 5:00 | 10:00 |
+---+----------+----------+---------+-----------+
I need to calculate the time spend in Location [A] between Arrival time on one date to the Departure time on the next date.
Please let me know what you think the optimal solution is to this problem, I am open to anything!
+--------+----------+---------+-----------+------------------------+
| Date | Location | Arrival | Departure | Time Spent in Location |
| 1/1/18 | A | 8:00:00 | 16:00:00 | 8:00:00 |
| 1/2/18 | B | 8:00:00 | | |
| 1/3/18 | B | | 18:00:00 | 34:00:00 |
| 1/4/18 | C | 8:00:00 | | |
| 1/5/18 | C | | | |
| 1/6/18 | C | | 16:00:00 | 56:00:00 |
+--------+----------+---------+-----------+------------------------+
The post from above is dead accurate - The trouble I am having is from the time intervals for each location being different (and random). I am trying to simply have an additional column which calculates the time spent in each location - from there I will be collecting data on each location and how many hours will be spent there.
Also, a big THANK YOU for the help so far! I am shocked by how quickly comments were made - sorry for the time it took me to make the mock-up, hope it helps make my goal in this more clear.
Actual Snip from sheet

Answer 1

One possible solution is to use the following formula in E2 and copy down.
=IF(C3="",((A3+D3)-(A2+C2)),IF(D3<>"",D3-C3,""))
EDIT: D4-C4 changed to D3-C3 in formula above)
It works by combining the date to the time, doing a math operation as needed and then stripping it out. Tap in a couple of IF statements to deal with rows that are single line locations, or the arrival only. It also assumes the first entry cannot be a departure.
Credit to urdearboy for the correct custom formatting. You will need to format the cells of the column to be [h]:mm
OPTION 2
This assumes that locations can be repeated. The use of a helper column is used to create a unique combination.
In F2, use the following formula and copy down as required:
=COUNTIFS($B$2:B2,B2,$C$2:C2,"<>"&"")
The $ locking the cells is very important. Note how it creates an expanding range as you copy down.
now technically speaking you can combine the following into one monster formula, but it will be difficult to follow and therefore maintain if someone else has to deal with it or you come back to it at a much later date. So on that note I will break it into 2 more helper columns and formulas
In column G we will identify the first row where a unique location occurs. A unique location is created by compounding the location name and the unique ID number which is a count of how often it has occurred in the list so far. Ie. A1 is the first time there was an arrival at location A, E2 is the second arrival at location 2. In G2 place the following formula and copy down.
=AGGREGATE(15,6,ROW($A$2:$A$16)/(B2&F2=$B$2:$B$16&$F$2:$F$16),1)
Now that the arrival row is identified the same needs to be done for the departure row. The same formula can be used but change the 15 to a 14. In H2 place the following formula:
=AGGREGATE(14,6,ROW($A$2:$A$16)/(B2&F2=$B$2:$B$16&$F$2:$F$16),1)
Now that you have those locations identified, you can use the following formula to calculate time:
=IF(D2="","",(INDEX(A:A,H2)+INDEX(D:D,H2))-(INDEX(A:A,G2)+INDEX(C:C,G2)))
In the example, I placed it in I2 and then I copied F2:I2 down as required. but it could be placed in E2 and copied down just as easily.
If you do not want those additional helper columns in G and H, then you can substitute them into your formula for time and it will look like this:
=IF(D2="","",(INDEX(A:A,AGGREGATE(14,6,ROW($A$2:$A$16)/(B2&F2=$B$2:$B$16&$F$2:$F$16),1))+INDEX(D:D,AGGREGATE(14,6,ROW($A$2:$A$16)/(B2&F2=$B$2:$B$16&$F$2:$F$16),1)))-(INDEX(A:A,AGGREGATE(15,6,ROW($A$2:$A$16)/(B2&F2=$B$2:$B$16&$F$2:$F$16),1))+INDEX(C:C,AGGREGATE(15,6,ROW($A$2:$A$16)/(B2&F2=$B$2:$B$16&$F$2:$F$16),1))))
A tidied up version using the monster formula and therefore not needing column G and H formulas:
Remember to apply custom formatting to your time calculation column of [h]:mm