unholiday
/ˌʌnˈhɒlɪdeɪ/Definitions
1. noun
A day on which people do not celebrate a holiday or engage in leisure activities.
“She spent her summer vacation as an unholiday, doing chores and running errands.”
2. adjective
Not related to a holiday or festive occasion.
“The store was decorated with unholiday colors during the off-season.”