can i alter my light cycle slightly?

hey guys,
Can i alter my light cycle at all durin 12/12? I start a new job tomorrow and it means i cant be here for the lights comin on at 4pm,it'll end up being around 6pm when im home.will i be able to alter it straight to 6pm or should i do it gradually?say half hour a day?just dont want to come home to the light or anything else to of not come on properly etc
Thank you for looking.
Sorry if its a bit of a noob question
Nemesis

...why can't you just leave them on a timer to come on when your not home?
...if your stuck on switching light hours, give them a longer night period, never give them longer light hours.

they are on a timer anyway but im just worried incase something doesnt come on for whatever reason or the light blows etc.
So i can do it straight away by just giving it an extra 2hrs on its night cycle tonight for instance?
Thanks for your quick reply

...absolutely. Just be sure to give your ladies the extra darkness...all is well.

cheers mate, thanks alot

i have been leaving my lights onn 24 hours for the past 2 weeks, my plant looks like its grown.. should i change my time aswell and what light hours should i give it???