First, the quantity and quality of calories are important for both health and weight. You can not win without surplus. You can not lose without deficit. And the quality of the calories you consume will affect health and saturation which in turn will affect the amount you consume. In addition, the bioavailable calories you consume will vary by food and may also vary according to the individual (this is a profit and loss with more ease than others).
Then, we are bad historians. We may forget the portions, choices or both, not all the time, but definitely sometimes. We can not know what meals we have not cooked. And even if we cook ourselves, most will not weigh and count everything and the eyes are terrible in both.
And a recent study confirms some of the above, according to which researchers looking at myfitnesspal users found that the average user almost lost calories worth a meal a day (445). However, studies on the use of a food diary almost always indicate that they have significant gains in weight loss.
Personally, although I think it has an inappropriate vague sense of caloric intake, it is valuable (if you were in a foreign country and you did not know the exchange rate, the price tags would still be somewhat useful), more valuable is the use of the diary to remember that you are trying to eat stochastic and possibly different.
Human nature is what it is, without a system designed to consciously remind you to change the usual default behavior, most likely to switch to these behaviors, whether healthy or not, and a food diary, even if it is inaccurate, -time, will I remind you many times a day that you are trying to change.
Since you are not using your calendar as a tool of judgment as it is not meant to be there to make you feel bad about your choices, it will probably be beneficial and likely to benefit whatever you are watching (calories, macros, carbohydrates , anything else) and even if it is inaccurate, because it is a primary job to serve you as a reminder service, not as your judge and jury.