Kernrechtsfrage
Whether the cantonal court fixed the start date of the modified maintenance obligation arbitrarily by choosing 1 January 2003 instead of 1 January 2002.
Extrahierter Entscheid
The chosen start date was not arbitrary; given the income fluctuations and the general rule that modification should not retroact, fixing the change from 1 January 2003 was defensible.
Extrahierte Begründung
The court noted substantial income fluctuations over several years and only a clear downward trend in 2003. Under the doctrine and equitable considerations, a prospective adjustment was permissible and not manifestly untenable.