Some basic calendar info:

There are three primary calendar types in the world: Solar, Lunar, and Luni-Solar.

In a lunar calendar, months are determined by the moon's cyclic phases. A new moon signifies the beginning of the month, a full moon the middle. The new year is determined by the ending of the 13th month, placing the new year ten days ahead each year. This calendar was/is more relevant in terms of hunter-gatherer societies.

In a solar calendar, the new year is determined by the arrival of a specific date in a fairly rigid cycle of light and dark - the solstices and equinoxes. This calendar payed close attention to seasons and light levels in the year, and is/was therefore more relevant to agricultural societies.

The Luni-Solar Calendar takes both the solar and lunar years into account when calculating a date. The solar calendar is used as the foundation, since it is more fixed than the lunar calendar. The lunar calendar is then overlayed and synchronized with the solar calendar.

In the solar calendar, the winter solstice is the time when yin reaches its utmost and gives birth to yang, and the summer solstice is the utmost of yang and the birth of yin. The equinoxes (days of equal light and dark) are times when yang and yin are equal. In the chinese calendar, the are considered the MIDDLES of the seasons, rather than the beginning and ending of seasons. Hence, the spring equinox is the middle of spring - the time when yang and yin are equal. Since each season is three months long, the equinox is placed at the 1.5 month mark. Counting backwards, this puts the beginning of spring (the chinese solar new year) on February 4th.

In the chinese calendar, the new year is calculated by "synchronizing" the two calendars - that is, the lunar new year is annually reset to the new moon closest to february 4th.

A new year where the new moon fell on february 4th would be considered a perfectly syncrhonized (or balanced) year. This is rarely the case, and most years have either a few extra or a few less days than the balanced year. Up to a month can be added or subtracted from the year. When a month is added, it is called a "leap month." Since months are lunar, a leap month must therefore fit into a season, meaning one season has an extra month. Likewise, seasons can have missing months. This is where the excess and deficiency of years and phases (also known as elements) comes in.

If a year has a extra days, it is a yang year. The phase of the year is determined by the season which will have the extra days or month. If the year is missing days, it is a yin year. Again, the phase is determined by the season which is affected by the missing days.

So, every year is either yin or yang, and relates to one of the seasons or phases.
Originally, People simply worked off of the natural cycle. Eventually, a system was designed in which fit harmoniously, however this formalized calendar quickly went out of sync with the natural cycle. It is still the one in use today. The system is based on the combination of 10 heavenly stems (yin and yang transformations of the five elements) 12 earthly branches (generally symbolized by the 12 animals) for a total of sixty permutations.

So, yes, there is a difference between each year, season, month, and even time of day, however calendars are not necessarily accurate portrayals of the natural cycles. If you want to understand the synchronization between a person and nature, it is best to learn about the five phases, twelve meridians, and the principles of date calculation. The Nei Jing is one of the better sources, but don't discount modern astronomy, physics, and chronobiology, either.

That should get you started, at any rate.

CSP