If your Tomato Plant, which is an annual plant, were to be in its natural environment, growing outside, it would germinate in the spring, hit its vegetative growth period during summer and produce flowers in the fall.
For the purposes of indoor growth, we’ve got to adopt methods to essentially convince or trick the plants into behaving as if they are in a particular season, regardless of what the reality outdoors may be.
For example: Many growers use a 24 hour lighting cycle for the seedling phase and an 18 hour on and 6 hour off lighting plan for the vegging stage.
When you have achieved the desired size for your plant you can trick it to begin budding/flowering by changing your lighting plan to 12 hours on and 12 hours off. Your plant will now think it’s fall.
In a nutshell, you are creating your own grow seasons as a direct result of your manipulation of the lighting cycle for your plants. Have fun playing God!