day names should only apply to the "working day" or "daylight day" period and the "-night" suffix should be used for less ambiguity
"see you guys frinight"
"ah sorry i have a dinner on wednesnight but im free from thursday onward"
"im flying in on saturnight and out on monday, hopefully make it home on time for an important call monnight"

perhaps a "-morn" could also be used to separate the day into more even distinct periods