The Conception Calculator

Due on New Year's Eve: When Did You Conceive?

Due dates & conception. Updated . Calculated with the standard pregnancy dating method used by ACOG and the NHS.

A baby due on New Year's Eve (December 31) was most likely conceived around April 9 of the previous year.

Due dateDecember 31
Most likely conception dateApril 9
Likely conception windowApril 6 – April 12
Estimated last periodMarch 26

Only a small share of babies arrive on their exact due date, so a holiday due date is a target rather than a promise.

Use the conception date calculator for your exact dates.

Conception Date Calculator: Find the most likely conception date from your due date.

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This article is general information, not medical advice. Talk to a doctor or midwife about your own pregnancy or fertility.