I'm not a fan of that wording as well as not a fan of making games be commitments where "I HAVE to be online on this particular day at this particular time". Everyone should feel an equal longing to play at any time. Also, not everyone has weekends on saturday / sunday, it would not be possible to satisfy everyone with this type of system.
Now, if we make larger clan groups reap more rewards for the entire clan. That's something we can talk about This gives incentives for people to all login at a particular time to gain rewards for everyone, even the clan mates that can't make it at specific times.