Why do you need to make the effort to tell people individually or repeatedly? Setup your calendar to auto-reject meeting invitations with a polite message that

Why do you need to make the effort to tell people individually or repeatedly? Setup your calendar to auto-reject meeting invitations with a polite message that you no longer work Friday and if your attendance is required for the meeting then please schedule for Mon-Thurs during your working hours. I do this with my non working hours, I book a block of 'out of office' time which auto rejects meetings and notes my normal working hours for the inviters future reference.