If you're looking to take a trip or twelve in 2018, but want to save some cash, these are the days you should take those trips.

According to Kayak.com, under their "Travel Hacker" section, they've put together a list of days that are the cheapest to travel via flight, both domestically and internationally. The results are based on 2017 data.

January

Domestic: Jan. 31

International: Jan. 19

February

Domestic: Feb. 7

International: Feb. 3, 21

March

Domestic: March 7

International: March 19

April

Domestic: April 29

International: April 27

May

Domestic: May 2

International: May 4

June

Domestic: June 3

International: June 2

July

Domestic: July 4, 18

International: July 31

August

Domestic: Aug. 29

International: Aug. 21

September

Domestic: Sept. 26

International: Sept. 25

October

Domestic: Oct. 31

International: Oct. 29

November

Domestic: Nov. 30

International: Nov. 11

December

Domestic: Dec. 10

International: Dec. 2

It also says that if you're flying out of North America, the best time to book is one month out.