Tell them you have a religious obligation at your church on day X.
Using religious excuses for certain days off every week is a strong excuse to avoid inconsistency in your life.
I worked in a fast food court on the Ohio Turnpike (i80/i90) and the weekends were always the busiest. This excuse always ensured my Sundays off, lightening my load on the week’s peak.
Got a DnD campaign in the evening on a weekday? You are busy with a church service you must attend.
Employers must make reasonable religious accommodations. Use it and protect your leisure!