Sorting a sheet via 2 columns by times in 2 columns with blank cells in certain cells

Have tried to sort this sheet example via columns J first ascending and then by columns F ascending with excels sort function but
due to the blank cells in column F at the top and column J at the bottom though, I get quite a mixed up sheet.

How would I go about sorting this sheet with the first priority being:

If column F is blank and column J has a time in it, I'd want that data at the top of the sheet.
Next criteria I'd want is if both columns F and J have times in them, I'd prefer both columns sorted in ascending order with column F being priority ascending followed by column J ascending.
Lastly if column J has no times in cells, I'd like the data at the bottom of the sheet.

Any ideas or even better a macro, it's beyond me..