Birthdays!

I have a character who was born on the Fourth of July! Unfortunately he's terrified of fireworks X'D Canonically he's going from eighteen to nineteen by the end of the story….dang, he seemed so old when I first invented him lol

I give all my characters birthdays, sometimes there's significance but mostly there's not.

Ara's birthday is on the 29th. I'm not sure how old he'll be turning because I haven't quite figured out how old he'd realistically be but I've put him somewhere either in his late 20's or early 30s. His birthday actually falls on national coffee day which is fitting for him.

All my characters have birthdays, some are chosen after family and friends but others are just random.

Zenith doesn't have a birthday. He was spawned in a lab as the first artificial life form and no one ever told him his spawn date. He wasn't considered human. However, he does know that he's approximately 15.

Yeah, I sort of assign them by picking a zodiac sign then just picking whatever date within the range feels right.

My antagonist’s birthday was two days ago, and one of the supporting characters has a birthday coming up October 8th.

Lysander's birthday is tomorrow and he'll be 16.

most of my characters have random birthdays, but I picked their star signs first, so their birthdays fit around those. I have two Scorpios (willow and benjamin), a Pisces (sicily), an Aquarius (gabriel), a Gemini (eli), a Leo (parker), a Taurus (grey), a Virgo (landon), and a Cancer (quincy)

I do give them birthdays/zodiac signs because I feel as an author my characters should have stories and lives as real people do.

Same here. Most of the time, my characters birthday's don't even really make it into the story. I think the only exceptions (so far, at least) are Dallas (January 7th) and Matthew (October 28th). For Dallas I needed him to turn 18 so that he would legally be considered and adult and wouldn't need his parent's permission to do a lot of things. With Matthew, I needed an excuse for a big party at the beginning of the story and a birthday was the best thing I could come up with.

Giana's birthday is the only one really mentioned because her turning 19 is what makes her and her sisters (plus Lucas) leave for the Woods.

One of my characters is asked during the story, "Why are you so happy?"
Instead of answering the question, she laughs and says, "My Mamma always told me that I was born with the fireflies and couldn't help being happy!" Born with the fireflies= born sometime when fireflies are out… Summer to early fall. Thus I chose her birthday to be June 2nd.
Really don't stress it. It can be really important in a story- Like someone prophesied that they would be born on that day. Or it can be not even mentioned in the story. Take into account whether you want their birthday to occur in the story or not. If your story is happening in the winter, the birthday can't be in may- you have to adjust accordingly. Or the birthday can just add a little endearment to a character- see my example!