How does my calendar know my birthday?

On iPhone, Apple's Birthdays calendar displays dates saved in Contacts, so your birthday can appear without a separate Calendar entry. If it's your own date, check your contact card, including My Card. Google Calendar and Outlook also use contact birthdays; the source depends on which calendar you're viewing. See Apple's birthday calendar instructions, Google's explanation and Microsoft's guide.

Check where your own birthday is saved

Start with the date that surprised you, rather than changing settings for every birthday.

1. Open Contacts on your iPhone.
2. Tap My Card at the top of the list, then Edit.
3. Look for your birthday and compare it with the date in Calendar.

Apple documents these controls in its My Card guide. Your card can contain birthday information as well as your name and phone number.

For someone else's birthday, open their contact card and tap Edit to inspect the saved information. Apple's contact editing guide lists birthdays among the details you can update.

A matching date gives you a source to investigate. It doesn't tell you when the birthday was first entered or who entered it. If there's no matching date on that card, check which calendar contains the entry before assuming it came from Contacts.

Why a date you don't remember entering can be there

Contacts can hold information from several accounts, including iCloud, Google and Microsoft Exchange. A birthday may therefore be on a contact you already use through one of those accounts. Apple explains the account options in its Contacts account guide.

With iCloud Contacts enabled, contact information stays up to date across devices signed in to your Apple Account. That makes a date saved on another device a possible explanation, rather than proof that it was entered on this iPhone. See Apple's contact sync documentation.

If you're using another calendar app, check its source too:

The Google and Outlook routes are documented in Google Calendar Help and Microsoft Support. For Google setup, see how to add birthdays to Google Calendar.

Hide birthdays or change the saved date

These actions solve different problems. Hiding removes birthdays from your calendar view; editing changes the source information.

To hide Apple's Birthdays calendar on iPhone:

1. Open Calendar and tap Calendars.
2. Deselect Birthdays.
3. Confirm the selection; Apple's support instructions call this Done.

You can select it again to show birthdays. These controls are covered in Apple's hide and unhide instructions.

For a wrong contact-sourced date, open the person's card in Contacts, tap Edit, correct the birthday and tap Done. To remove that source date, remove the birthday information from the contact card. Apple explains that its Birthdays calendar is updated through Contacts in the Mac Birthdays calendar guide, and documents iPhone contact editing in the Contacts guide.

Check one entry afterward before changing the rest of your list. If you're trying to keep birthdays visible, our iPhone Calendar birthday guide covers the setup.

Check duplicate birthdays and alert timing separately

For duplicates, search the person's name in Contacts and compare any matching cards. Apple specifically recommends checking for multiple contact cards when a birthday appears more than once. See its duplicate calendar events guidance.

For birthday reminder timing, go to Settings → Apps → Calendar → Default Alert Times → Birthdays, then choose an option. Apple documents that setting in its Calendar settings guide.

If the date is correct but an alert is missing, use the birthday reminders troubleshooting guide to check delivery settings.

Keep a separate list in Birthday Countdown

If you'd rather choose which birthdays to track manually, Birthday Countdown keeps a separate list on your iPhone. It doesn't import birthdays from Contacts or Calendar, and it doesn't sync between devices. Each entry shows the days left, with the next birthday at the top.

To add someone:

1. Open Birthdays and tap + at the top right.
2. On New Birthday, enter First name, which is required, and select the day and month.
3. Open Reminders, tap +, configure a reminder and tap Save Notification.
4. Add optional groups or a note, then tap Save Birthday.

Reminders can be on the day, 1 day, 3 days or 1 week before, or a custom number of days. You can choose the time and add more than one reminder per birthday. They're local iPhone notifications, so notification permission is required.

Birthday Countdown is free for up to 5 active birthdays; unlimited birthdays require Premium. It stores the day and month without a birth year or age, and you don't need an account.