Heya Gangaman84!
Nice looking plant! Since you have mentioned it is a photoperiod plant and not autoflowering, it won't begin its flowering stage until the days reach 12 hours of darkness or less. Your plant will continue to vegetate until around October when the days are shorter.
When it is flowering you want to judge harvest time off the colour of the trichromes. You can use a jewellers loupe or small microscope to see the trichromes. When the trichromes are clear you want to wait a bit longer. When they are milky white it can be harvested and will produce more of a head high. OR, you can wait until 30% trichs have ambered which creates a more body high. You can also have the balance in between as well.
If judging by pistils only, usually you want to harvest when 70-90% of the pistils have browned or turned orange.
Cheers and goodluck mate!