The state Reapportionment Commission has scheduled a special meeting next week to correct an error in the way the state’s 25 Senate districts were split into two- and four-year terms, affecting two districts.

Senate District 11, currently from Lower Makiki-Punchbowl and represented by Sen. Carol Fukunaga, was originally to be a two-year term, but now will be for four years in 2012.

And Senate District 22, the current Kaena-Wahiawa-Pupukea seat held by Sen. Donovan Dela Cruz, will be a two-year term when it is decided in 2012, instead of a four-year term.

In all, 12 seats will be up for two-year terms in the next election to stagger the 25 seats and ensure that only about half come up for re-election every two years.

The split is determined by a mathematical formula designed to ensure that every senator serves two four-year terms and one two-year term in a 10-year period. Some serve the two-year term at the front end of the decade, the rest at the end.

Voters approved the method in 2000. Four-year terms are assigned to Senate seats where a majority of that district’s voters, under the new redistricting plans, were represented by a senator who served a two-year term before reapportionment.

Conversely, if a majority of voters in a new district were represented by a senator who served a four-year term before reapportionment, that district would be assigned a two-year term.

The error occurred because a 2010 Senate election for District 11 that was decided in the primary was not previously counted. The state Reapportionment Commission approved Monday the new maps and the plan for staggered terms.

The oversight was corrected the following day. It now must be approved again by the commission.