Experts say that's when caregivers are most like to shake a baby -- sometimes to death.
Four-month-old Dylan always has been cute but not always quiet.
"He would cry about 3 hours, between 3-4 hours every night for a few weeks," explained Stephanie Bias, Dylan's mother.
"I definitely got frustrated several times," admitted Eric Bias, Dylan's father.
They admit they almost lost it.
"I've said several times I would never shake my baby, but I completely understand the levels of frustration that well up inside of you to stop this level of crying," Stephanie said.
Stephanie and Eric credit the Period of Purple Crying Project and DVD for helping them keep their cool. It's a 5-year program being implemented at hospitals and birthing centers across the state.
Right after giving birth, nurses teach parents that it's normal for babies 2 weeks to 5 months old to cry, sometimes for hours and sometimes for no reason.
"This is a normal period, and it's a matter of all of us learning how to cope with that so we don't in a moment of feeling frustrated and overwhelmed, damage these babies," Child psychologist, Doctor Robert Murphy, explained.
Doctor Murphy heads the program that is teaming up with Duke and UNC to reduce the rates of shaken syndrome through education.
Murphy says 40 babies die each year in NC from being shaken. A study shows more than 2,000 children in the state under the age of 2 are shaken each year, often ending up with serious injuries that can change their lives.
"Blindness is common, developmental delays, mental retardation, kids may have learning disabilities," Murphy said.
When parents are about to reach that boiling point, experts say the best thing you can do is set your baby down in his or her crib, make sure it's clear and then walk away. Give yourself time to calm down so you don't hurt your baby.
That's advice the Biases say they followed and shared with other family members and caregivers to protect Dylan.
The Biases want all new moms and dads to know the Period of Purple Crying does come to an end.
"At the 3 month point he just did a 180 degree turn," Eric said. "He just seemed to be a different person."
Stephanie agrees. ""We have a happy baby now and that's something we weren't sure we were going to have."
For more information about the Period of Purple Crying and tips on how to soothe your baby and how to handle stress, click here.