combine data associated with multiple date/time columns

[dannybten23]

I have 4 sets of columns. each has a date and time in column one, and a number in column two. the dates and times are close, but are not the exact same. I want to add the numbers of all the non-date columns that are closest in time. i.e. i want all the numbers that are close to noon on the 15th to be added, and all the numbers that are close to 1:00 on the 15th to be added and so on. Example attached. Any suggestions will be greatly appreciated.
Very Respectfully,
Dan