Macbook calendar won't sync to my Iphone calendar

Hey there, and welcome to Apple Support Communities applestudentlearning,

We can certainly understand your concern and can help provide some insight.

We recommend checking out these steps on troubleshooting sync issues with iCloud Contacts, Calendars or Reminders.

"  Learn what to do if your iCloud Contacts, Calendars, or Reminders aren't appearing on all the devices that you use with iCloud.

Things to check first

1. Check the system status of iCloud Contacts, Calendars, or Reminders for services outages or connection issues.
2. If a reminder isn't showing up on some of your devices, make sure that your iPhone and iPad have the latest version of iOS or iPadOS, or that your Mac has the latest version of macOS.
3. Make sure that you're signed in to iCloud with the same Apple ID on all of your devices. Then, check that you turned on Contacts, Calendars, and Reminders in your iCloud settings.
4. Check that the date and time settings on your device are correct for your current location. 

Try the steps for your device

If you still need help, try the steps for your device below.

• iOS and iPadOS
• watchOS
• macOS
• iCloud.com
• Microsoft Windows

iOS and iPadOS

After each step, check your contacts, calendars, or reminders. 

Restart the Contacts, Calendar, or Reminders app

1. Close the app.
2. Return to your Home Screen.
3. Wait about one minute, then open the app again.

Refresh your contacts and calendars

To refresh your contacts, open the Contacts app and swipe down on the list. To refresh your contact groups, tap Lists in the upper-left corner, then swipe down on the list. 

To refresh your calendars:

1. Open the Calendar app.
2. Tap the Calendars tab.
3. Swipe down on the list to refresh your events."

For additional information check out this link: If your iCloud Contacts, Calendars, or Reminders won’t sync - Apple Support

These steps will help ensure your device is working with ease and can fix common issues like the ones you’re experiencing.

Kindest regards!