The Monday more formal calls 星期一> 周一>礼拜一（方言）

礼拜一 is normally used by local people, 周一will be more formal. We also use 星期一 as another formal call. Hope this helps.

“周一” is more formal

Thanks all :)

Surely 周一 is formal. 礼拜一 is not supposed to be used in any formal notice or document. Actually 星期一 is the right word in formal documents.