Event reminders by calendar, email, text or app push, compared

The short answer

An event in someone's calendar sits there from the day it's added, and their calendar app can alert them before it starts. Email and text arrive the moment you send them, and app push does too once someone has your app on their phone. Studies have found text and email reminders getting more people to clinics, gyms, courts and polling places. None of them tested calendar events, so the research can't rank calendars against the other channels.

How do the channels compare?

	Calendar event	Email	Text message	App push
What the customer does first	Connects their calendar or subscribes to a calendar link, once	Gives you an email address	Gives you a mobile number	Installs your app and turns on its notifications
Where it shows up	In their calendar app, as an event with its own alert	In their inbox	In their messages	As a notification from your app
When it reaches them	The event is there from the day it's added, and the alert goes off ahead of it	When you send it
If the plan changes	A connected calendar updates the event. A subscribed one waits for the app's next refresh	You send another message
What you can measure	Taps on tracked links in the event	Clicks. Opens overcount readers on Apple Mail	Taps on tracked links	Taps, in your app's analytics
Research on attendance	None we could find	Gym visits up 13%. Voting unchanged by campaign emails, up slightly with emails from a county registrar	Clinic no-shows at 15% with reminders, 21% without. Missed court dates down 21%	None we could find

What does the research say about each channel?

Most of the studies we found tested text messages, each in one setting. A 2016 review of 21 clinic studies, all using SMS, found patients who got text reminders were 25% less likely to miss appointments. In New York City, texts in the week before a court date cut failures to appear by 21%, according to a study in Science. Text reminders also raised the likelihood of voting by 3.0 percentage points in a 2006 US election experiment. Among patients with a doctor's visit coming up in fall 2020, flu shot texts lifted vaccination by 2.1 percentage points, or 5%, on average.

The email studies point in different directions. Weekly reminder emails raised gym visits by 13% among members of a Swedish health club, and the rise held for three months after the emails stopped. In voting, 13 field experiments with 232,716 people found registration and turnout “unaffected” by email campaigns. Emails sent by a county registrar in California raised turnout by a small amount, and the same words from a fictional group had no measurable effect.

For app push and calendar events, we didn't find a published study of their effect on attendance. Our roundup Do reminders reduce no-shows? gives each study with its setting.

What does a calendar reminder do differently?

The reminder comes from the event itself. Once a business's event is in someone's calendar, their calendar app shows an alert before it starts, at the time set on the event or at the person's own default. The details stay in the event, links included, where people see them whenever they look at their week.

A subscribed calendar can lose its alerts. When someone subscribes in Apple Calendar on a Mac, Apple's guide says they have to deselect the Remove checkbox to keep the calendar's alerts, and there's an Ignore alerts option as well.

How the event got there also decides what happens when you change it. In a connected Google or Microsoft calendar the event changes within moments, alert included. A subscribed calendar shows the change after the app's next refresh, which can take hours, and our guide on why a subscribed calendar isn't updating has the timings app by app. An event someone saved from an “Add to calendar” button stays as it was, as our guide to buttons and subscriptions explains.

Which channel fits which job?

A season or schedule you set weeks ahead. Put it in people's calendars once, and every date is there when they plan.
A plan that changes on the day. A connected calendar moves the event itself. Send a text or email as well if people need to hear about the change before they next look at their calendar.
Offers and news. Email has room for them. Judge it on clicks, because Apple Mail Privacy Protection hides who opened, as our guide to what it did to open rates explains.
Customers who already use your app. Push asks nothing new of them.

To learn what works for your own events, send a reminder to a random half of your list and compare attendance with the other half.

Where TheyCal fits

We make TheyCal, and it covers the calendar column alongside the emails and texts you already send. Followers connect their Google or Microsoft calendar, or get a private calendar link for Apple Calendar and other apps. The business picks the alert for each event, from 10 minutes to a week before, and can add a second one. Outlook calendars get only the earlier of the two. Links in events are click-tracked, which shows a business the events people tap through from.

The Reminder menu on a TheyCal event form, open to show choices such as 1 hour before and 1 day before — In TheyCal, each event carries its own calendar alert.

Common questions

Do calendar reminders work better than email?

We couldn't find a published comparison, and we haven't published data of our own. A split test on your own list is the way to find out.

Should I still send email reminders if my events are in people's calendars?

Email reaches people who haven't put your events in their calendar. For those who have, send the email to half of them and compare turnout to see what it adds.

Can I tell whether someone looked at a calendar event?

TheyCal counts taps on the links in an event. It has no way to tell whether someone looked at the event itself.

How many reminders should I send?

The clinic review found multiple notifications “significantly more effective at improving attendance than single notifications,” and the best program in the 2021 flu study reminded patients twice.