Good Sign - Flowers

 Seeing flowers on new tomato seedlings while working with hydroponic semi commercial crops, was the indicator they could be placed on the slabs. The home gardener will see the same thing, that flowers are the indicator to make sure they are planted in the garden at this stage.

Assuming this variety of tomato will produce ripe fruit in 65 days, it's from the flowering stage to the ripe fruit stage that's called "Days to Maturity" stage.

All tomato seed packets will tell you how long until maturity, which is how you work out when to expect ripe fruit.