IMO, better than using a clock or calendar to determine when you add nutrients you should use your hydrometer - and so if you are using this protocol (TOSNA) you are in fact adding the nutrient as the yeast deplete the available sugar at 1/3 depletion, at 1/3 again, and at 1/3 again (so, if SG was 1.105 then first addition is at 1.070, second is at 1.046 and third is at 1.030 approx. Adding nutrient when the yeast are unlikely to take up some of the nitrogen, for example, can lead to off flavors., however I generally add all the nutrient at the very start.