For those with a regular 9 to 5 work schedule, experts recommend napping no later than 4 p.m., as a late nap can interfere with your sleep cycle. Napping late in the day means you might not be able to fall asleep at your regular bedtime, causing exhaustion the next day. The point of a nap is to make sure you are well-rested, so taking a nap too close to bedtime could defeat the overall purpose.