Which calendar date did Samoa skip when it moved across the International Date Line in 2011?

Samoa skipped 30 December 2011 when it moved across the International Date Line.

At the end of 29 December 2011, Samoa advanced its clocks and calendars directly to 31 December. The change moved the country from the American side of the International Date Line to the Asian side, aligning its working week more closely with key trading partners such as Australia and New Zealand.

As a result, Samoa celebrated New Year's Eve on 31 December 2011 after having no local calendar day dated 30 December. The change did not mean that time itself stopped; it changed which civil date was assigned as the country moved through the time-zone boundary.

Samoa had previously changed in the opposite direction in 1892, when it observed 4 July twice. Tokelau made a related date-line change at the same time, but it is a separate territory and should not be substituted for Samoa in this question.