The universe as observed by us is intricate and varied, however, there is a widely accepted rudimentary inception to our convoluted present. The conception is that all energy existed at a single point and expanded into disparity. Entropy is a measure of disorder within a system, as the universe expanded and disorder increased a direction in time is avowed with increase in entropy.

 The initial properties of the universe are established as having perfect order and thus the instance of time is implicit. It follows that the established initial conditions also hold the attribute of being static in time, that is, infinite.

The direction of time, if remaining constant, will unavoidably reach another extreme. This is not chaos as is oft inferred by applying the principle of entropy, consider instead the 2nd law of thermodynamics which states,

"The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium."

The notion of maximum entropy being at equilibrium is a definitive representation of order. Thus we have the defining end of time as absolute symmetry, which necessarily implies a static superstate akin to one at the start of time. A situation such as this will occur if the temperature of the universe is at absolute zero, this is in fact where the universe is observed to be progressing towards.

The consequence of this understanding is that the universe as we perceive it has a fixed beginning and end to progressive time. Now that a measure of the extremes has been derived let us consider the progress between them.

The initial state is one type of order, this order is that of sets or groups (it being a single condensed uniform group of everything). A group is a collection of entities that have some form of equality, they can be observed as they stand out due to their uniqueness such as: stars, carrots, catholics, atoms or peanut butter jars. We recognise groups of stuff readily consider the string "CCCCYYYY!!!!". The final state of order is one of perfect symmetry, we perceive symmetry in shapes, gas in a fixed volume or in mixing up a cocktail to form a liquid of equal consistency - "CY!CY!!YC!YC" displays a vertical symmetry. Varying degrees of these orders describe the intermediate states of everything in the universe. Progress through time is in fact one type of order changing to the other.

Consider turning peanuts into peanut butter,

Start with groups of peanuts and butter, then blend them into an halfway mixture of chunks of peanuts and a uniform peanut-butter mix (if you like it crunchy!) or to a single 'smooth' state. Note that once the mixture is blended there is no way back to the original nuts and butter.

There does not have to be a one-way direction for instance randomly mixing up, "AABBAAABBA", for many iterations will still have a random result. Yet there is no way to change from one position to the next without taking a step that is closer to either superstate of order. Also note that complexity arises by virtue of the intermediate states, we exist in a period of mixed order and thus complexity. Merging stuff that exhibits different order allows complex structure such as those found nature - cells, skin etc.

It is clear how the transformation from one state of order to the other is dominating nature - a gas will evenly fill a space it is released into - as our universe will eventually expand to a size so large that all matter will be smeared out into invariable space.

To get a clearer idea imagine crushing a can of paint on a flat surface and then evening out the splatters of paint until the surface is evenly coated. The surface also curves and flexes under the paint and expands constantly - perfect symmetry will occur when the surface stretches to infinity in all directions. This final state seems impossible to reach as it does not exist in our assessment of time.

The picture we have of time is but a small portion of the superstructure of spacetime. In understanding the static nature of the extremes of order one must realise that time is not a single dimension or straight line progression, as it contains something that is invariable that must exist perpetually. If you consider our normal idea of time:

Start|----<past---------------now---------------future>-----|end 

there is no scope for a static point. Adding a dimension at right angles at every position along our timeline allows 'real' time to be a static structure. Each possible point in time is described by this coordinate system, every possible next instant is a position on the vertical axis. We experience just one position on 'y' for one position on 'x'. The time we perceive is a ripple along this static superstructure and we are unaware of the larger and unmoving actual dimension - that is, our view of time is in fact amiss. This implies that every instant in time already exists and that it may well be possible perfectly predict the future, this is not the case. All points in time do exist, however, there is an infinite number of pathways from one state of order to the other and the pathway we take is not predictable. There is an infinite number of succeeding points to any given position and the laws of nature constrain which of those are possible. Hence there is no way to determine which will occur, conversely looking back in time can not be predicted precisely as there are (vastly) more than one valid positions that could lead to the current point, although again we know that the defining laws must be obeyed. Note that the start and end positions of order are identical in every position along the vertical dimension of time.

There are many plausible routes from one state of order to the other, perhaps in both directions and some may even revert back on themselves. This would cause a flip in the direction of time (reversed time is not as odd as you may suppose, it is just a tendency to group order. Nearly all the laws of physics do not have a preference to the direction of time besides the middle states between the orders will show the same type of phenomena). The fundamental constants on our timeline may well be completely different to others allowing such things as a collapse.

If you would like to know more (and better!) I would suggest looking up no-boundary model as proposed by Stephen Hawking and also the book "Everything Forever" by Gevin Giorbran. I have not read either beyond a summary and most of the above are my understandings, thoughts and misconceptions on their models.