Tried to clean it up at the end but there doesn't seem to be a way to clear "Null" values from "Time" data types within Data Cleansing tool.
Tried various ways in the expression writing within Formula to do "simple" math expression for converting Sunset to 24 hrs, didn't work and included some odd outputs. Knowing what I am trying to achieve through saying it and then having to write that down in the expression editor is vastly different.
This seemed such a simple exercise when first reading it but the amount of tools i used confirmed otherwise.....i need to quicken up on these challenges!!