Closest Palindrome From Date | Dataford Interview Questions

Elsevier content systems may need to identify dates with symmetric YYYYMMDD representations for indexing and validation. Given a valid Gregorian date in YYYY-MM-DD format, return the closest different date whose eight-digit YYYYMMDD representation is a palindrome.

Search by calendar-day distance. If two palindromic dates are equally close, return the earlier date.

Formal Specification

Implement closest_palindromic_date(date_string), where date_string is a valid date from year 0001 through 9999. Return the closest different valid date as a string in YYYY-MM-DD format. The palindrome check must ignore the hyphens and use exactly four year digits, two month digits, and two day digits.

Constraints

date_string is a valid Gregorian date in YYYY-MM-DD format
0001 <= year <= 9999
The input date itself must not be returned
At least one different valid palindromic date exists within the supported range

Function Signature

def closest_palindromic_date(date_string):

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