It was Christmas Eve.
Speedy and Boomer were about to start their new job.
The two reindeer looked around the warehouse.
They saw a huge, pretty sleigh.
Colorful presents filled tall shelves.
Elves scurried around everywhere.
"Hey there!" said a friendly voice.
Speedy and Boomer turned around.
"I'm Rudolph," said a reindeer with a shiny red nose.
"I'm the reindeer in charge.
Our job tonight is to pull that sleigh through the air."
"That sounds easy," said Boomer.
Rudolph nodded. "It's not hard.
But our boss, Santa, has lots of stops to make.
We'll stop at millions of houses all over the world."
"Whoa!" Speedy gasped. "One night isn't enough time!"
"Don't worry," said Rudolph.
"We will have 24 hours of night."
"Huh?" said Boomer. "How is that possible?"
Rudolph led Boomer and Speedy to a giant map.
"Earth is divided into 24 time zones," said Rudolph.
"Because there are 24 hours in one day?" asked Speedy.
"Right," said Rudolph.
"The sun only shines on one side of Earth at a time.
So it's always daytime in some places and nighttime in others."
"Let me show you."
Rudolph pressed a button.
A big part of the map went dark.
"When it's 11:00 p.m. in Japan, it's only 11:00 a.m. in Argentina," Rudolph said.
"Argentina's time is 12 hours behind Japan's."
He pressed another button.
A zigzag line appeared.
"This is the International Date Line," said Rudolph.
"Each day starts here.
We'll start at this line and fly west."
"How long will we spend in each time zone?" asked Speedy.
"One hour. Then we'll move west to the next time zone," said Rudolph.
"Oh! The time will be one hour earlier there!" said Boomer.
"Exactly!" said Rudolph.
"We should get ready.
We have 24 time zones to visit!"
"That's a lot of flying," said Boomer.
"I'm going to get hungry."
"Many children leave treats for us," said Rudolph.
"But watch out—the boss usually eats them all!"