Starting on January 18, Disneyland will be offering a series of after-hours events called Disneyland After Dark.
The first one is called "Throwback Nite" and it taps into early Disney nostalgia:
Step back in time to the ‘50s and ‘60s for a taste of the classic after-dark experience at Disneyland. Come dressed in your best to enjoy the Happiest Place on Earth under a million twinkling lights, swinging to the tune of the bands and enjoying your favorite rides in the cool moonlight ‘till the clock strikes 1 a.m.!
Original attraction posters of Disneyland experiences from yesteryear welcome you as you commemorate the evening with special photo locations... Live music and dancing bring the bygone era to life throughout the park, and the sky lights up with an exclusive showing of “Fantasy in The Sky” fireworks. Guests will receive a commemorative lanyard and a vintage-inspired park map that will highlight the special experiences taking place throughout the evening.
It sounds to me like a nighttime, sanctioned version of the popular Dapper Day, ie. it sounds like fun!