[urgent]How to switch to flowering

They're currently on a 17/7 light schedule. Should i let them 27h in the dark, and then switch to flowering, or 30h with light and then switch to flowering?

dude i say just put it into 12/12 if u leave it in tha dark for two dayz it wont do any good i think i does cause a bit of stress for them so i say just swich

I need them to get light from 8pm to 8 am. I'm switching to the hps, and i'm already having temperature issues with the mh

There's no need to put your plants in darkness for ant extended period of time. Simply switch your timer over to 12/12. If your having trouble maintaining your temperature, simply ventilate the room better. A good CHEAP way of doing that is to go to Wal-Mart, buy a ceiling vent fan for a bathroom, and some 4" foil duct. Mount the fan Near the top of the room, and it will pull some of the hot air out. Hope I helped.

The next time your lights are on, leave them on for 12 hrs and go from there.

Again, i need them to be on from 8pm to 8am. I already have an extractor, andn will upgrade soon, but not soon enough. Thank you anyway. If anyone else could help me i'd apreciate. (i also have very high humidity during the night ~70-80%

If you need your lights to be on from 8-8, than buy a timer, and set it to 8-8... And if your having trouble with humidity, move more air,(buy more fans) or get a dehumidifier.

I would go to 12/12 first, then move the on off time forward or backward a half hour a day until you are at 8 and 8.

dude , 12 ON 12 off ! there u go its done

I think HE thinks we are telling him to put his plants on a 12pm 12am sched... get a timer put the on time to 8pm and the off time to 8am, that way you get your 12 hours on from 8pm to 8am pretty easy. I wouldn't worry about turning the lights off for 30 hours or whatever crazy number you said... lower your Humidity by venting more. what time is your 17hour lighting start at? run your lights from the start of your 17 hour start til 8am then do the switch, i would imagine that this way would shock the plants less, or do the thing the guy above me posted