Days of the week conditions

Hello,

I am trying to create a template for my work. I have a table sorted by dates but need to reference the day of the week that date falls on. If the date falls on Sunday-Wednesday I need the value to be "X" if it falls on Thursday-Saturday I need it to be "Y". Is excel smart enough to recognize days of the week from a date format? And what formula would I use to accomplish this result?