This is a great question, and one we figured that some of the big generic survey tools must have already answered.
So we did some Googling, and found... a lot of disagreement!
SurveyMonkey says the best day to send invitations is Monday
CheckMarket also says Monday
But TypeForm says Tuesday to Thursday!
To settle this, we took a deep dive into our data.
We reviewed almost half a million feedback requests, and found:
The best days are Tuesdays, Thursday or Fridays
Avoid the weekends - Saturday was the worst day, followed by Sunday
Mondays also get a lower response rate - around 75% compared to over 80% on Tuesday, Thursday and Fridays.
The best day to send out invitations for your project may well be different. You'll
also want to consider:
Are there any reasons that a lot of people might be off work or unable to check email? (e.g. because of holidays or training)
Are there any other announcements, deadlines, or other distractions that could make this a bad day to send out the invitations?
Of course, the day that you send the original invitation is only one factor in getting a high response rate.
To get the best response rate for your project, check out our guide: How to get a 99% response rate