Recently my company sent me to a different city to attend a conference for a 6-day trip, which also included two days on the weekend.
I was asked by my manager to participate in 16-hour “volunteer” meetings by the conference organizers during the weekend, and do not charge the company because “we are paying for your accommodation and sending you to the conference.”
He seems to think that on my weekends I have nothing better to do on my personal time then to “volunteer” on behalf of the company and do not charge time to the company.