The biggest time difference between two places on earth is a whole 26 hours. The Howland islands, an unincorporated unorganized territory of the United States, use a time zone of -12 hours UTC on the far west of the earth. The Republic of Kiribati’s Line Islands, which have a time zone of +14 hours UTC, are on the far east of the earth. These two places, therefore, have the biggest time difference of 26 hours.

Source: World Atlas