Hi @sladerose,
Just in case: you may not need an API for that.
Option 1: you can use value from Date & Time → Current Time, formatted as Day of Week. With this you get day name (e.g. Monday, Tuesday, …). Then you can use various ways to set up further logic based on that.
NB: this works if your users use one language, because formatted value will depend on user’s device language settings (e.g. different for English, French, …)
Option 2: you can determine the day of week ID using several math formulas. See the post here How to derive weekdays from a date and here Show information exclusively on a specific day of the week.
Best,
Victor.