Had to edit the whole thing as it was a stupid question once I read it back!
Apologies!

OK as I have got more posts on this than on more serious topics I guess I should!

So my lights are 18/6 running from 12pm to 6pm. I want to start flowering and run lights from 7am to 7pm and I was going to ask if today I should run the light from 6pm to 7am and then start 12/12 OR to keep in darkness (they have been in dark since 12pm today) until 7pm tomorrow.

I just figured not wasting peeps time and just start at 7pm tonight my 12/12

that a propper question..thats okay, you can go to 12/12 with light or dark, its the end of 1 cycle and start of another.

Takes days for the plants to notice the nights have got longer.

If changing the time in flowering (e.g. if you've forgotten the clocks go back next weekend), best to have a longer night than a longer day ...