Depending upon the weather and light, they use the day light to not only see the sources of food they need, however also use the sun to aid their navigation. As a result, when it gets dark, they tend to return to the beehive. If you were to move a beehive to another location, its best to close the hive up at night so you can be sure most of the bees from that hive are inside and back home. This minimises loss of orphaned bees.