Cook Islands changed its date from the west (Asia, New Zealand, Australia) side to the east (American) side on Christmas day 1899. In 1899 the Cook Islands celebrated Christmas twice to correct the calendar. According to the old books, missionaries were unaware of the International Date line, when they came from Sydney. Thus the Cook Islands were one day ahead. ".... The Christmas Day Act was designed to change the time to that of Tahiti and all other civilised places east of the 180th degree of longitude: it is a measure that has been strongly opposed by the Maoris on previous occasions ..." (Lieut-Colonel Gudgeon, 14 Sep, 1899) See references below: Discoverers of the Cook Islands and the Names They Gave (Victoria University of Wellington) Christmas Day Act 1899 http://nzetc.victoria.ac.nz/tm/scholarly/tei-KloDisc-t1-body-d18.html (page 60) PACIFIC ISLANDS. PROCEEDINGS OF THE BRITISH RESIDENT, RAROTONGA. (National Library of New Zealand) Appendix to the Journals of the House of Representatives, 1900 https://atojs.natlib.govt.nz/cgi-bin/atojs?a=d&d=AJHR1900-I.2.1.2.3 (page 20) I guess, Zone Pacific/Rarotonga was +13:20:56 before Christmas 1899 and on Christmas Day 1899 time zone has been changed to -10:39:04 (text Christmas Day Act 1899 on our web site): https://www.worldtimezone.com/dst_news/dst_news_cook-islands01.html (or Christmas Day Act 1899 screenshot): https://www.worldtimezone.com/images/1899-cook-island.gif Regards, Alexander Krivenyshev, https://www.worldtimezone.com