Clear Blue Digital Ovulation Test Detects The Rise Of The Ovulation Hormone Lh (Luteinizing Hormone) 24-36 Hours Prior To Ovulation And Identifies The 2 Best Days To Conceive In A Given Cycle. ItS More Accurate Than Calendar And Temperature Methods And Gives You Unmistakably Clear Results On A Digital Display.The Unique Feature Is That It Is Smart Enough To Adapt To Your Personal Cycle By Giving You A Clear Smiley Face In The Result Window When Your Lh Surge Has Been Detected To Identify Your 2 Best Days To Try For A Baby.