Day name short -

[pluckannfeel]

can you put a function where the week days text will be formatted with one letter
e.g : S M T W T F S

[richardtallent]

Using the weekdayNameFormat: "narrow" option. It will remain localized to the user's chosen language setting, but will be as narrow as possible (for English users, it's one letter).

If you need to override the user's language preference or you need to support very old browsers, you can use the option dayNames: ["S","M","T","W","T","F","S"] and it will use those names.