Unique Half-Hour DST Step

Lord Howe Island: The World's Only 30-Minute DST Shift

Winter Standard: UTC+10:30 (LHST) Summer Daylight Saving: UTC+11:00 (LHDT) Jurisdiction: New South Wales, Australia

Worldwide, every jurisdiction that enacts Daylight Saving Time (DST) shifts its clocks forward by 60 minutes in spring and back 60 minutes in autumn. Lord Howe Island, situated in the Tasman Sea 600 km east of mainland Australia, is the world's sole exception: it advances its clocks by exactly 30 minutes.

Mount Gower and Mount Lidgbird rising high above the pristine lagoon of Lord Howe Island
Lord Howe Island's 380 permanent residents switch between UTC+10:30 and UTC+11:00 each season.

Why a 30-Minute Adjustment?

Lord Howe Island lies at longitude 159°05'E. During standard winter time, it sits at UTC+10:30 (half an hour ahead of Sydney, which is at UTC+10:00).

In summer, when the state of New South Wales advances its clocks by one hour from UTC+10:00 to UTC+11:00, Lord Howe Island chooses not to shift a full hour (which would put them at UTC+11:30). Instead, the island moves forward only 30 minutes, harmonizing at UTC+11:00 and synchronizing perfectly with Sydney during the tourist peak summer season.

Software Engineering Headaches

Operating systems and global time libraries like Linux tzdata and Microsoft Windows include custom algorithmic exceptions specifically for the "Australia/LHI" entry because it violates the assumption that all DST transitions are integer 60-minute jumps.

Explore environmental and astronomical background at the Lord Howe Island Board Official Portal.