Unless it is an “auotflower” strain, flowering time refers to when the plant gets 12 hours of uninterrupted darkness, so outdoors, this means late fall/winter most places, near the equator the day vs. night is about 12 hours each all year long. Flowering is usually referring to an indoor grow and starts the first day the plant gets the 12 hours of uninterrupted darkness and as such is a loose guide or approximation of time until finished. Auto flower strains need a good amount of light their entire life and from seed to flower takes only about 3 months or a bit longer depending on the auotflower strain and will flower even if given 24 hours of light their entire life. Regular long dark cycle/winter flowering strains will not flower and will continue to grow as long as they are getting a lot more than 12 hours of light, most indoor growers using 18 hours of light and 6 hours of darkness to simulate spring/summer.