Ijet lag
Izowuni zexesha ziinxalenye zelongitudinal kumphezulu woMhlaba phakathi kweemeridians ezimbini ezikhethekileyo, ezisebenzisa ixesha elifanayo ngeenjongo zomthetho, ezoqoqosho nezentlalo. Ngaphambi kokwamkelwa kwabo, ixesha lelanga lendawo (umyinge okanye inyaniso)
) lisetyenziswe kwiindawo ezahlukeneyo zoMhlaba.
Imimandla yexesha, ngokudibanisa ibhendi okanye indawo yendawo yexesha, ivumela iiwotshi zommandla okanye ilizwe ukuba zimiselwe kumndilili wexesha lelanga le-meridian esembindini yendawo ewela kuyo. Ekuqaleni, ihlabathi lahlulahlulwe layimimandla yamaxesha angama-24, indawo nganye eyayigubungela i-15° yobude, yayinezowuni yexesha layo yaye yahlukile kummelwane wayo ngeyure enye. Emva koko, ubukhulu becala ngenxa yezizathu zezopolitiko, iindawo zexesha ezingama-39 zenziwa, ezisasetyenziswa nanamhlanje.
Iindawo ezininzi zexesha ziyaphambuka kwi -Coordinated Universal Time (UTC) ngenani elipheleleyo leeyure ukusuka e-UTC-12 (i- Baker ne- Howland Islands) ukuya kwi-UTC+14 (i-Line Islands); abanye, nangona kunjalo, banokutenxa kwe-30 okanye i-45 imizuzu (njengexesha lexesha laseNewfoundland yi-UTC-3:30 kunye ne- Nepal UTC + 5:45).
Amanye amazwe asebenzisa ixesha lokonga imini kwinxalenye yonyaka, ngokuqhelekileyo elitshintsha ixesha ngeyure. Iindawo ezininzi zexesha le-terrestrial zitshintshelwe ngasempuma ukusuka kwiindawo zazo zexesha le-nautical ezihambelanayo; oku kudala isiphumo esisisigxina sokugcina ixesha lokukhanya kwemini.