I really think it depends where you live. I water my tomato plants once a day although some people on the internet say a deep water weekly.
If you have good soil that doesn't drain away too quickly, look at the plant to know. If the leaves begin to droop, then you need to water. They are quick to recover. I will say, I seem to have the best results watering in the early evening.
Good luck, I hope you have a bumper crop.