This is "To the Ends of Time", a low-budget made-for-tv film from 1986.
The film's review in Variety ticks all the right boxes:
Set in a fantasy world where sailing ships fly and benevolent rulers
protect their kingdoms with strange weaponry, “To the Ends of Time” is
a fairy tale about the clash between time, humans’ greatest enemy, and
their most potent force, love.
Tired of watching “pain, death and destruction,” the monarch is
determined to end war forever, calling upon the magical powers of his
alchemist, Aeschylus (Michael Silverback), to find the right solution.
After many sleepless nights, Aeschylus presents a most original
device: time. Whoever controls time, he reasons, will be the master of
the universe. With this powerful device, the victor can watch his
enemies age and die before their time. Before long, every human in the
world is aging at the alarming rate of one year per week, a giant
clock ticking away relentlessly inside an extinct volcano.
Following the format and archetypes of fairy tales, yarn’s witch is a
black-haired sorceress named Karnissa (Sarah Douglas) who kills
Aeschylus, steals his plans and orders her followers to build the
monstrous device he’d invented.