When do amateurs operate?

Practically anytime.

Hams can operate day and night, summer and winter, weekends and weekdays. They operate when driving, boating, flying, and walking; during breaks at work or school; when relaxing at home, camping in the wilderness, sitting in the park, commuting to work, and traveling on business or pleasure.

Ham radio is versatile and can be incorporated into many other activities.

Being able to set aside an entire afternoon, evening or weekend may be wonderful, but it is not required. Ten minutes over lunch hour is plenty of time to make several short contacts.