freecodecamp--freecodecamp/curriculum/challenges/english/blocks/daily-coding-challenges-python/6a2037a68a0bc2aef0006003.md

id, title, challengeType, dashedName

id	title	challengeType	dashedName
6a2037a68a0bc2aef0006003	Challenge 341: Birthday Countdown	29	challenge-341

--description--

Given today's date and a birthday, return the number of days until the person's next birthday.

• Today's date is given as a string in "YYYY-MM-DD" format, with leading zeros, for example: "2026-07-16".
• The birthday is given as a string in "M/D" format, without leading zeros, for example: "9/7".
• If today is their birthday, return the number of days until their next birthday (not 0).
• Leap years should be accounted for.

--hints--

days_until_birthday("2026-07-16", "9/7") should return 53.

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(days_until_birthday("2026-07-16", "9/7"), 53)`)
}})

days_until_birthday("2026-07-16", "3/22") should return 249.

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(days_until_birthday("2026-07-16", "3/22"), 249)`)
}})

days_until_birthday("2026-07-16", "7/16") should return 365.

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(days_until_birthday("2026-07-16", "7/16"), 365)`)
}})

days_until_birthday("2024-02-28", "3/1") should return 2.

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(days_until_birthday("2024-02-28", "3/1"), 2)`)
}})

days_until_birthday("2023-04-24", "12/30") should return 250.

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(days_until_birthday("2023-04-24", "12/30"), 250)`)
}})

days_until_birthday("2024-03-01", "2/29") should return 1460.

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(days_until_birthday("2024-03-01", "2/29"), 1460)`)
}})

days_until_birthday("2096-03-01", "2/29") should return 2920.

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(days_until_birthday("2096-03-01", "2/29"), 2920)`)
}})

--seed--

--seed-contents--

def days_until_birthday(today, birthday):

    return today

--solutions--

def days_until_birthday(today, birthday):
    from datetime import date

    year, month, day = [int(x) for x in today.split("-")]
    b_month, b_day = [int(x) for x in birthday.split("/")]

    today_date = date(year, month, day)

    def is_leap_year(y):
        return (y % 4 == 0 and y % 100 != 0) or y % 400 == 0

    def next_valid_birthday(from_year):
        for y in range(from_year, from_year + 9):
            if b_month == 2 and b_day == 29 and not is_leap_year(y):
                continue
            d = date(y, b_month, b_day)
            if d > today_date:
                return d

    return (next_valid_birthday(year) - today_date).days