Most places and communities in Faerûn seem to be using the Calendar of Harptos. A calendar that divides the year into 12 months of 3 tendays each, and a total of 5 holidays mushed between some of these months.
The Sword Coast Adventurer's Guide has a neat sub-chapter on said calendar in Chapter 1 ("Welcome to the Realms"), detailing the above information: "Time in the Realms"
But, there seems to be no further information regarding single days. Being Central-European (and living in a Christian country), I am used to the idea of our Monday to Friday being days when most people work; Fridays are days where piety is shown by consuming fish, Saturdays are somewhat divided, and Sundays are for church and family.
What (if any) official WotC source(s) contain information on the meanings and uses of weekdays?