recurring event on calender

When planning an event ie a holiday it is always good to know what my day off at work would be for the week in question. I have a rolling day off on a four week cycle. Because we work Saturdays I work what is called a one in four - which unfirtunatly means I get one in four Saturdays off not that I have to work one Saturday in four. My days of occur as follows: Sat/Mon/Thurs/Fri and the fifth week becomes the Saturday again. It is tediously long to go through the calender manually putting in every day off. I have looked at using the custom setting to set up each day off in the cycle. This works fine for months that have four weeks but some have five and thows the recurring off. Is there any further custom setting that I can use so that all my rest days are automatically entered? Thanks in advance.

I use an ipad (purchased new this year) and iphone 7 plus.