/* Using the relation that has all your food entries*/
prop("Food Entries")
/* Filtering to get only the ones that match with the Date property*/
.filter(current.prop("Date").formatDate("DDMMYYYY") == prop("Date").formatDate("DDMMYYYY"))
/* Select the property "Approx. Calories" and get the sum*/
.map(current.prop("Approx. Calories")).sum()
Made by lth_29