Every garden has a light cycle. Depending on what stage your plants are in (flowering or vegetative) you will need to set up your lighting to turn on and off at the proper intervals. You need to understand how this works if you are going to succeed and get a solid harvest out of your garden.
In nature, outdoors, plants follow the seasons and while water and temperatures can play into this, the length of day also sends signals to the plant. As the summer turns into fall and fall turns into winter the days get shorter and the nights get longer. In your indoor garden you control the seasons by using a timer with your light to control the day and night length.
Some plants decide when to flower based on the length of the day / night cycle. Plants such as lettuce flower when the nights get short; plants like cucumbers will flower when they are large enough regardless of the length of the day or night.
Cannabis plants flower when the days get short and the night gets long. Cannabis determines this cycle based on the amount of dark time it receives every day. For proper vegetative cycle you need to have more than 12 hours of darkness and less than 12 hours of light- 18 hours of light is recommended, followed by 6 hours of darkness. For flowering Cannabis 12 hours of darkness and 12 hours of light are required. You can set up your LED grow lights on a timer to make the light and darkness fall any time you want in the day. This allows you to have the lights on when you are most likely to have time to care for your garden.
The longer you leave a Cannabis plant in the vegetative state the larger it will get. You can keep a plant in the vegetative state for extended periods of time either waiting for it to get to the size you want for flower or to keep it as a mother plant which can be used to take clones from. By using a mother plant for clones you can save a significant amount of time versus growing plants from seeds every time. It also allows you to keep growing a favorite plant over and over again.
When the plants are the right size you can transition to flower from the veg stage and this is where things get exciting. The plants grow more rapidly and require more attention and this is also the most important time in terms of affecting your yields.