Date of issue: 1 January 1908.
“These stamps were used by the Shackleton Antarctic Expedition of 1908. The 1 penny universal stamp was overprinted ‘King Edward VII Land’ by Coulls, Culling & Co.”
– from New Zealand Post website

“Lieutenant E H Shackleton, R.N.R. (later Sir Ernest Shackleton), had intended making his base camp in King Edward VII Land in the Antarctic but on failing to find a suitable landing place he made his base at McMurdo Sound, which was in fact in Victoria Land. The Expedition left England in the ‘Nimrod’ on 7 August 1907. Its last port of call en route to Antarctica was Lyttleton, New Zealand, where final departure for the southern continent was made on 1 January 1908. Lieutenant Shackleton was appointed to be a Postmaster by the New Zealand Government and was provided with a special date stamp – the date stamp read “Brit. Antarctic Expedition” in a circle with “NZ”, time and date in four lines in the centre.”
– New Zealand Post website