How can I sum values over a range of dates in Numbers?
It works by dereferencing the value of a cell directly to the condition
Example:
SUMIFS(Daily Log::Income,Daily Log::A,">=2014-07-01",Daily Log::A,"<2014-08-01")
Referencing the cell could also be made possible with the same construct; by adding ampersand followed by the cell name outside the double quotes.
Example:
SUMIFS(Daily Log::Income,Daily Log::A,">="&A3,Daily Log::A,"<"&A4)