Daylight time based on dates


Hey fellas… I found a pretty cool website that can help out with outdoor grows I think. You just input the year and the location and it generates a chart showing how many hours of daylight each day of the year has. This could be beneficial for warm weather folks to get a look and see if they have time for a late season grow.

oh,…and yeah…it’s official government info, lol.

I noticed in my area… if someone had seed germinated and sprouts in the next couple of days… they could get in 30 days of veg growth before the daylight started to dip below 12 hours.


Such a great post! I planted 4 seedlings outside at the beginning of the month. I only did it because I had thrown some bag seeds into germination and when they germed I figured I had to grow them now haha. My dad also wanted a plant for him being grown outside, and I have 2 outdoor gardens, so again, I figured I had to grow them there!

3 went into my big garden with veggies. And one went into the small raised garden bed that I have. So far, the 3 in my main garden are thicker and slightly larger than the one in the raised garden bed.

I only thought they would be able to veg outside for a month or so, but after using the link you posted I see that I have until September 25th until it’s 12/12 lighting. Basically they have another 4 weeks until the switch, which will give them time to grow big and thick.

Thanks for posting this @oak!


glad it was useful… I am expecting seeds any day now… was planning to just grow autos but had considered trying a fem seed as well which is why I went looking for the info… not sure I will have enough time… is 30 days of veg enough time?


It should be OK with strong plants. Any that struggle may come up short. I wouldn’t do any cropping or anything that may slow them down. The real deadline to watch is early freezes.


The outdoor girls. They’re all completely organic, with zero added nutrients. Just germinated, sprouted, transplanted outdoors when they were 5 nodes tall. The garden soil is just amazing I guess? I plan on giving some nutrients soon though, but didn’t want to press my luck, they look so beautiful already and I’d hate to mess anything up!

This one is in the raised garden bed. She’s the smallest.

And these 3 are in my main garden. They’re much thicker in stem size and leaf size.

Hoping they’ll get bigger before flower starts. And then hoping they’ll be able to finish flower before frost hits!


true. Generally speaking it does not freeze around here until at least Thanksgiving… the idea has me spending time looking for a fem or photo that flowers out in around 8 weeks, lol… I guess if it were close I might be able to bring her in for the last couple weeks.


Autos definitely the only way now.


I’m sure they will have a decent go. You probably get October frost don’t you? We get early frost end of October sometimes, definitely first of November.


Good info on the hours in a day chart. Good Looking Out…


Looks like I will hit 12 hours on Sept. 26th. Just how sensitive is the plant to that schedule? The day before only has 2 extra minutes.

Is that the date I should expect to start counting my flowering days? Or will that start the typical 2 week preflower stage?

If I can flower up until the first frost, I should be good until late December/early January. More than enough time on that end. Would have been nice to have had more veg time.

Next year…!


The plants develop or reduce certain hormones in reaction to the photoperiod (length of light vs. dark). This is not an instant action. This builds up slowly over time as a reaction to changes in the the photoperiod.

Also some indica, and obviously ruderalis autoflower hybrids will react differently than many equatorial sativas. Some indicas can start to flower with as little as 8 hours of darkness, and some sativas can require as much as 13 hours of darkness.

So, the direct answer to @FloridaSon 's question, is it is not that sensitive and the 2 minutes longer the day before doesn’t make that much difference. The hybrid’s unique qualities and the way it reacts to your climate will even change the way the same strain grows and flowers at the same latitude but with a different climate.

It is the latitude and the way the earth tilts on its axis towards or away from the sun that determines the length of day or night in your area, it is also why areas in the southern hemisphere have the opposite season to the northern hemisphere, as that side of the globe is facing at an angle away from the sun.

In other words, this is why it is summer in Australia when it is winter in Europe, Asia and North America.

Happy growing,



There’s actually a discussion going on that could include the tilt of the Earth, but…

So from what you have stated here, which actually clarifies what I have seen in the past, I can’t schedule my plants by that information.

So at what point, after determining sex, would I begin to say “I’m in the preflower stage.” ? Does the simple fact that I am able to make that determination start my counting? And is the 2 weeks of preflower the same across strains, or is there a specific sign that will tell me this plant may require more or less than two weeks?

Being inquisitive can be a downfall for me sometimes. I’m probably making this more difficult for myself than it really is, but trying to learn this scheduling of the plant’s life cycle is seeming to stump me. Just trying to get as much out of them as I can. You know.

Thank you @MacGyverStoner. You’re always a great help!


Yeah, I’m in TN, and mine have been in flower for 2-3 weeks. Different strains, all photos.


Is it because they are autos? Or do you know?


No, these are photos. I’ve grown outside off and on for years in this area, and my plants always start flower well before 12/12 light date. And these have always been bag seed, or gifts from friends. I still can’t wrap my head around it. I think if given plenty of time, they complete their lifecycle when ready, but can be triggered to change to flower by limited light.


One of my outdoor plants is showing pistils now, and it won’t be 12/12 lighting for another 3 weeks. Either way, I’m happy haha


Hello, I have seen a similar discussion on outdoor flowering and daylight here. What is FLOWERING TIME to Harvest Outdoor Plants
There is another discussion here Timing for outdoor veg, flower and harvest This is also a great sunlight positioning guide.


Those are great discussions on this topic, thanks @bmorgil .

I’m aware of the other discussion. I’ll just paraphrase what was said in the other thread, I’d rather not attempt to debate it, I feel like it would be like trying to argue the finer points of calculus to a cat.

Depending on how the plant is growing, you might only get the flowering that directly leads to full flowering. Pre-flowering is dependent more so on the genetics of the individual plant. It is kind of like auto flowering, it happens at a certain age or development of the plant from seed. Sometimes certain stresses can also cause pre-flowering. The difference from regular flowering is it will not continue to aggressively flower if the light to dark period is not correct for that strain.

The photoperiod (length of light period per 24 hour day) is the main or strongest influence on when the plant flowers, but it is not the only environmental factor, temperature drops also can influence the same and similar hormones that the short photoperiod has an effect on.

@FloridaSon, here is a great you-tube video that shows how all this works and why 2 minutes, more or less, from one day to another isn’t all that important nor is it exactly what a day is in nature, and how longitude, latitude and the rotation of the earth are so important to sunrise and sunset:



My plant is starting to flower, she is more like a tree any ways my concern is with fall coming on and the temps starting to get cooler, how will this effect this stage of flowering??? Will I have to cover it or bring into the house???. I have frost blankets, this is my first time growing and have had great success, I am a active gardener and good at it. So can someone give me some input on this subject.


Where i live, this is the time of year your plants have been waiting on, its flower time almost. You have to keep check on temperatures for your area. If temps are expected in the frost zone you will need to cover during such periods. But you must remove frost covers first thing in the morning as well. Hope you the best!