3712315 - Why end dates differ when using duration in Days vs Months during Job Posting creation?

End date appears different depending on whether I enter the duration as days or months (e.g., 546 days vs 18 months result in different end dates in a Job Posting)

job posting duration, duration, end date difference, end date, difference, months vs days, calendar month calculation, date calculation, months, days, job posting creation, job posting, end date calculation, day count, adjustment, months, days , KBA , BNS-FG-JP-CRT , Job Posting - Creation , Problem