A general rule for the maturation of indoor growing to enable flowering is not time based as much as it is plant based.

Your plant will tell you its maturation level.

For flowering, look at the secondary growth shoots. Look for the alternating stems. Not the MAIN stem, but the grow shoots.

Look for the stems growing that alternate as opposed to growing at the same node height.

That is the sign of maturation for flower.

Attached is my plant SLUT. I ran out of room for her in my space....and since she hasnt shown sex, I had to pic her ass the one to toss.

But i too cant throw a good plant away, so I took covert action and planted her amongst some tall Lion Grass I grow in my backyard along a fence. The lion grass grows 8 FT tall and flowers in summer up to 12'.

I have her nestled deep in the back so she is invisible unless you part the lion grass by hand. I did sacrifice some sun for the clandestine aspects, so she has stretched just a tad...

The hard part is getting in there and taking a picture cuz I literally have to get on hands and knees and go into the grass to get a pic.

The dogs look at me very funny too....

Anyhow, if you look right at the middle grow shoot on the pic, you will see how the fan leaves begin to grow at 'alternating' spaces. Maybe a half inch between leaves...

Thats the sign of a plant being mature enuff to flower.