Bees are important pollinators and their presence in your vegetable garden is a good sign. Whether you want to observe them or avoid them, determining the time of day bees are likely to come to visit your garden will depend on several different factors.
Species of Bee
Several species of bee might like your veggies, so what time of day they come around depends on what type of bee it is. The most common kind of bee is the honeybee, and studies show that these pollinators like to go out during the midday around 1 or 2 p.m. But other types of bees may prefer a slightly earlier or later schedule; you'll even find a species of bee in Southeast Asia that only comes out at night.
Types of Plants in Your Garden
Bees are attracted to different species of plants. Sometimes they are attracted by color (which is why flowers are so pretty), and other times they may be drawn in by the familiarity of a particular species of plant. If you want bees visiting your vegetable garden more often during the day, try planting some flowers, herbs or berries that attract bees close to your veggies. Some examples include agastache (which also attracts hummingbirds), currant, snowberry or willow.
Time of Year
Bees love the warmer months, so you're much more likely to see them in the spring and summer. Bees prefer sunny areas to shady ones too, so if your vegetable garden is exposed to sunlight for a long period of time during the day then the window where bees are likely to show up will be longer. On the other hand, if your vegetable garden sits in the shade all day, then the bees may look for a more inviting place.
Bees like the sun, but in some climates they might be forced to work outside in harsh conditions. Amazingly, honeybees can withstand sub-zero temperatures if necessary (sometimes even as cold as minus-30 Fahrenheit). At other times, bees might have to work in extreme heat. Either way, when the outside temperature and conditions are less than ideal, then the time frame where bees will be out in your garden may be restricted to only the time of day that offers the best reprieve from the harsh climate (i.e., the bees may only come out in the cooler morning and evening if you live in a desert).