Light is the most important part of photography and landscape photographers use natural light. Light changes throughout the day so here is a guide to natural light.
Before the sun has even risen you have a time called blue hour. This is where the light has a very strong blue tint. If you don't have neutral density filters then this a great time to do some long exposure photography. You can also get some amazing colours in the sky before the sun has even risen. It is still a bit dark so you'll need a tripod or be leaning on something to make sure your photographs are sharp.
After the sun has risen you get golden hour. This is when everything is flooded by beautiful, soft golden light. It also has a slight red tinge to it. Not only is it a great time for landscape photographs but portraits as well.
As the day progresses the light is harsh and seems very white in colour. This begins not long after golden hour has ended. You'll find that your photographs will either have quite dark shadows or really bright highlights. Your camera isn't able to balance the light and dark areas in the scene so chooses one to be correct. These bright and dark areas make wonderful black and white photographs. All of these is especially more on days where there are no clouds.
Cloudy days will give you soft, diffused light. Perfect for portraits and close up photography as you have very few shadows. You will find that there isn't much contrast in your images though. This type of light can also be found in the shade. When there is a break in the clouds it can make some spectacular photographs.
Just before the sun sets we get golden hour again which is the same as golden hour in the morning. After the sun sets there is blue hour again. It is worth hanging around after the sun has set as there can be some lovely colours in the sky.
A few things note. Golden and blue hour don't actually last for an hour. By doing an internet search or use an app like Photographer's Ephemeris to find the exact times. Your eyes are much smarter than your camera. Your camera won't and can't see the scene in front of you the same as your eyes do.
Golden hour is definitely my favourite part of the day. What is yours?