Yes you can. To select the day(s) you wish your campaign is shown, please follow these instructions:
1. Go to: https://adf.ly/advertiser
2. Click on the little wrench icon on the right side of the campaign you wish to update.
3. Go to the 'Day Targeting' field and tick the box next to the day(s) of your preference.
4. Click the Update button.
Now the Status of your campaign will be 'Active' during the days you have selected. The rest of the days the Status will be 'On Hold'.