On iOS and macOS birthdays are duplicated I've been experiencing duplicated birthdays on my laptop and iphone and couldn't find the answer. Every time someone's birthday it says tomorrow/today *name's* birthday and one more tomorrow/today *name's age* birthday.
Found a problem that my google calendar got contacts' birthdays as well as iCloud and that caused duplication. 

Solved by simply unselecting google contacts calendar for contacts both on iPhone and MacBook in Calendar Preferences.