Its a different country, but the distance is so little that they made it only a half an hour time difference.
Nowadays they are a full hour apart.
However, not all places on an even hour’s time, GMT
Some places/countries use time offsets not an integral number of hours from UTC/GMT.
Newfoundland (Canada) is UTC/GMT - 03:30 (summer -02:30)
Australia (Northern Territory) is +09:30
Australia (South Australia) is + 09:30 (summer +10:30)
India is +05:30
Iran is +03:30 (summer +04:30)
Afghanistan is +04:30
Burma (Myanmar) is + 06:30
Marquises Islands is - 09:30
Norfolk Isl. (Australia) is +11:30
Lord Howe Island (Australia) is + 10:30 (summer +11:00)
Sri Lanka is +05:30
Some places use quarter / hour offset from UTC/GMT.
Nepal is UTC/GMT +05:45
Chatham Island (New Zealand) is UTC/GMT + 12:45 (summer UTC/GMT + 13:45 or winter in the northern hemisphere).
Western Australia, Eyre Highway towns: Eucla, Caiguna, Madura, Mundrabilla and Border Village (South Australia) use UTC/GMT +08:45