I've seen the days of the week abbreviated several ways, such as: a) Sun., Mon., Tues, Wed., Thu., Fri, Sat.; b) SUN, MON, TUE, etc.,; or more informally as c) Su/M/Tu/W/Th/F/Sa or d) S/M/T/W/T/F. A or D are probably the most common, with A being the most grammatically correct

As answered already by Joe, there are many ways. Once you decide to abbreviate something, there are no formal rules, as you will see many variations . The way it is abbreviated is often decided by the format or context of the writing. As a general rule, option A of Joe's answer is probably the most common.

As a native speaker, I would say Mon. is more representative of a good communicator of the English language. Hope that helps!

You've got some choices! Sun., Mon., Tue./Tues., Wed./Weds., Thu./Thurs., Fri., Sat. Or if you're making a list: Su, M, T, W, Th, F, S Sometimes Thursday has been abbreviated as R, though this is less common. Likewise, some institutions will abbreviate Sunday as U, but again this is not very common.