UNDATED -- UPS says today's peak shipping day will be the busiest in its history.
The men and women in brown will deliver 28 million packages in the U.S. That's about 300 parcels every second!
UPS is so busy, the company is removing some delivery guarantees, according to this message on their website.
"Due to holiday volume, UPS Ground delivery guarantees are suspended until December 26, 2012. All other guaranteed UPS Services will be delivered within 90 minutes of the normal commit time."
Tomorrow is the deadline to for Christmas Eve delivery.