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Code reviewMediumcr-g344
Subject Date arithmeticLevel Mid–Senior~18 minCommon in Code quality & review interviewsIndustries Software development

Question

Review this Python that advances a monthly subscription's billing date by one month.

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Separate real bugs from style. Rank issues by severity, point at the root cause rather than the symptom, and suggest a concrete fix — specific and kind.

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Code to reviewpython
from datetime import date def next_bill(d):    # d is the current billing date, e.g. date(2026, 1, 31)    month = d.month + 1    year = d.year + (month - 1) // 12    month = (month - 1) % 12 + 1    return date(year, month, d.day)
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