Pregnancy Age Calculator Pregnancy Age Calculator Calculate pregnancy age between two specific dates. 1. First Day of Last Period (LMP) JanuaryFebruary MarchApril MayJune JulyAugust SeptemberOctober NovemberDecember 2. Calculate Age On (Target Date) JanuaryFebruary MarchApril MayJune JulyAugust SeptemberOctober NovemberDecember Calculate Pregnancy Status Pregnancy Age on Target Date - Trimester - Due Date (Fixed) - Progress on Selected Date