I'd create a series of tabs with the janitor numbers, business hours, public holidays

then create some columns with formula that give 0 if the data is invalid or 1 if it is valid (either on this sheet or another one).
check janitor number, check business hours, check weekend/public holiday, check if double,maybe check if over 24hrs (although this is probably OK).

then one more column to calculate the times it is on based on the criteria (ie the time between valid "ON" s and the corresponding previous off i suppose)

Then a table to sum and display the result.

Exactly how this would look depends on the format of the data you get for business hours etc and how you want the result displayed.