I would not rely on a pre-determined quantity of water as a guide post for your daily consumption. You have to be aware of your body's needs throughout the day.
Is it a workout day? Are you doing cardio more than weights? Was your job particularly active today? Did you exhaust yourself with a vigorous roll in the hay with the girl in your avatar? Did you drink any alcohol today? How many supplements or medications did you take? Are any particularly dehydrating?
Are any diuretics? Are you at any part of the day in or near ketosis? Do you eat alot of salt? Were you out in the sun much?
Those are just some of the things to consider when judging whether you need more or less water at any given time. Urine can be a fairly good yard stick also. Are you going moderately frequently (about every 2 hours) with decent volume and is the urine fairly clear?
When in doubt, drink more water.