With a sufficiently long period, the time of day does not matter. A positive result will still appear, as the “pregnancy hormone” literally skyrockets. However, at the initial stages, the level of hCG fluctuates during the day: in the first half of the day, the concentration of the hormone is maximum, it gradually decreases. Obviously, it will be most effective to do the test in the morning. Daytime and evening results may be false, as there will be little hormone in the urine.
If you "dilute" the urine too much, that is, drink a lot of fluid, the kidneys will be loaded with work, and this will ruin the test. So it is better to drink a little before taking it at night. Diuretic drugs are prohibited. The test is best done immediately after the woman wakes up and goes to empty her bladder for the first time, then the concentration of hCG will be the highest.