Let's talk first about how to divide the day into four stages, which we can then use to talk about life stages and seasons. First is morning, from sunrise until the sun peaks in the sky. Second is afternoon, perhaps until about 4:00 pm. From that point until twilight we have late afternoon and early evening third. Finally, when the sun is gone, it is night.
The morning corresponds to spring. There is dew upon the grass and the world seems to have a fresh energy, a sense of renewal. There is a sense of possibility in the spring, as there is in the morning, and birds seem to sing more in the morning, much as they seem to in the spring.
The afternoon corresponds to summer. There is growth in the day, work to be accomplished, and not yet a feeling of tiredness, although at the peak of summer, on those very hot days, a siesta is a good thing.
The late afternoon and early evening is autumn. There should be a kind of harvest feeling to the day, a reaping of the rewards for a day of work, a way to enjoy the fruits of one's labor. Of course, the day has peaked and energy is waning. The air is cooling, and the year is beginning to wind down. People are closing up their day with various rituals, much as nature is beginning to shut down for its long winter sleep.
Finally, in winter and at nighttime, we and nature sleep, restoring energy for the spring, healing any harms done by the day.
Dividing our lives into only four stages is somewhat arbitrary, but I would say that from infancy to perhaps late adolescence would be morning. This is a time of great energy and growth. Second might be the early twenties to the fifties, a time of work and consolidation of growth, just as the afternoon is. The late afternoon until twilight is the time in our lives when we reap the benefit of our labors and then begin to wind down our lives as death or night comes to us.