The tower lights up every year from Oct 9 (John Lennon's birthday) till Dec 8 (the anniversary of his death). It's also illuminated from Dec 21 (Winter Solstice) to Dec 31 and the first week of spring (Mar 20 - 27). In tribute to Yoko Ono, it also lights up on Feb 19, the date of her birthday.
It's lit from one hour after sunset till midnight (until dawn on New Year's Day). On Oct 9th and in March it lights up at 8 p.m.
Official Website http://imaginepeacetower.com/
Coordinates 64°9'47.79" N -21°51'33.383" E