Bobcats are primarily crepuscular. In other words they are most active in the few hours before and after sunset and sunrise.
This form of activity does not apply to all bobcats all the time. There are exceptions. Some studies have found that bobcats are primarily nocturnal. Other reports have stated that they may be active at any time of the day. Other reports say that they are arrhythmic (without any routine of regularity).
It is reported that in some areas bobcats are more active during the daytime in winter. This is probably because they must spend more time searching for food.
When daytime temperatures are above 26°C (78.8°F) the bobcat may be provoked into more nocturnal activity.
Finally, in most studies the bobcat’s pattern of activity seems to coincide with that of its major prey. Its major prey depends on its location. It is usually the white tailed deer, cottontail rabbit, marsh rabbit, snowshoe hare, black-tailed jackrabbit and unknown lagomorphs (pikas, hares and rabbits).
Hope this helps.
Source: Wild Cats of the World.