Not to be altered; immutable

the unchangeable seasons.

not changeable or subject to change; "a fixed and unchangeable part of the germ plasm"-Ashley Montagu; "the unchangeable seasons"; "one of the unchangeable facts of life"[ant: changeable ]

adjective

changeable , changing , inconstant , intermittent , temporary

adjective

changeless , continuing , firm , fixed , immovable , immutable , inalterable , inevitable , inflexible , invariable , irreversible , permanent , resolute , stable , strong , unalterable , unmodifiable , unmovable , ironclad , rigid , absolute , adamant , adamantine , consistent , constant , dependent , eternal , implacable , inalienable , inconvertible , inexorable , intact , intractable , monolithic , pristine , sedentary , sessile , stabile , static , stationary , steadfast , stereotyped , stubborn , unchanged , uncompromising , unfaltering