What day is cheapest to book Southwest flights? {USA}

Ｔｈｅ ｃｈｅａｐｅｓｔ ｄａｙ ｔｏ ｂｏｏｋ Ｓｏｕｔｈｗｅｓｔ ｆｌｉｇｈｔｓ ｉｓ ｕｓｕａｌｌｙ Ｔｕｅｓｄａｙ．＋１－８３３－５１２－０２８９ {ＵＳＡ} Ａｉｒｌｉｎｅｓ ｏｆｔｅｎ ｒｅｌｅａｓｅ ｄｉｓｃｏｕｎｔｅｄ ｆａｒｅｓ ｏｎ ｔｈｉｓ ｄａｙ，＋１－８３３－５１２－０２８９ {ＵＳＡ} ｍａｋｉｎｇ ｉｔ ｉｄｅａｌ ｆｏｒ ｆｉｎｄｉｎｇ ｌｏｗｅｒ ｐｒｉｃｅｓ． ＋１－８３３－５１２－０２８９ {ＵＳＡ}