Calculating Time Slots

Can you attach a sample file with some data and expected results?
That way we know what the format looks like and we can offer up correct formulas.
Calculate the result manually and enter it.

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Hello rmhodson1 and Welcome to Excel Forum.
Wish that I could think of an easier way of accomplishing the goal, perhaps someone will be able to improve on this.
As modeled in the attached copy of the file G7:P7 is populated using the dates, G8:P9 is populated using shift times* and G10:P12 is populated using:

Formula:

=IF($D10>G$7+G$9,"",ROUND(MIN($C10-SUM($F10:F10),(G$9-G$8)*24,IF(F10="",(G$9-MOD($D10,1)),1)*24),2))

*The first shift (Tuesday - Friday) is shown as running from midnight through 16:00 then the second shift from 20:00 to midnight.
The 'End Date and Time' values are populated using:

Formula:

=MAX(INDEX(G10:P10,MATCH(0,G10:P10,0)-1)/24+INDEX(G$7:P$7,MATCH(0,G10:P10,0)-1)+INDEX(G$8:P$8,MATCH(0,G10:P10,0)-1),INDEX(G10:P10,MATCH(0,G10:P10,0)-1)/24+D10)

There may be a way to (semi) automate the populating of dates and times if the overall method is of any use to you.
Let us know if you have any questions.