changing light cycle?

Hi there thank you for reading post.

Ill get to it i wanted to know if i could chane my 18/6 light cycle. still keep it in 18/6 due to semi middle of veg, just change it to a diffirent time period. like know my light turns on at 12am turns of 6 pm and so forth. so will changing this to start and end at diffirent times hurt the plant?

Thank you again!

if you want to change the start time just give them darkness until you the time you want...them turn the lights back on. more darkness is ok