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According to Einstein we live in a universe made up of fixed blocks of space-time while defining the change brought on by time in terms of our movement through each successive block. However, it is also possible it is not the result of us moving THROUGH them but IN them.
But before we can continue, we must first define what time is.
Some define it only in the abstract saying that is an invention of the human consciousness that gives us a sense of order, a before and after so to speak. However, many physicists define it in terms of the physical properties of a space-time dimension.
Yet, the observable properties of time are something that most of us can agree upon. 
One of the most persistent is that it is not directly perceived as matter or space but as a physical, chemical, and biological change in physical space.
One reason why most humans perceive time as only a measure of sequential ordering of change MAY be because similar to length it is perceived only as measurement of where in relation to arbitrary reference point in space an object is located. Putting it another way time MUST be define as measure of when an event occurred with respect to an arbitrary reference point attached to the sequence of the events it is a part of.
As was mentioned earlier Einstein define the passage of time in terms of our movement through successive fixed blocks of space-time.
However, this means your birth death and every other moment of your life is out there in space-time waiting for you to arrive.
This also suggests that free will does not exist because your future is etched in a block of space-time waiting for you to move through it and there is nothing you can do to change it.
Yet, he provided another way to explian
the past, present and future when he derived the energy required for them to occur in terms of a dynamic interaction between space and time. This is because it gives us a way to define how and why change occurs in terms of us moving IN space and time instead of moving thought static ridged blocks of it.
One can understand why by using an example of two dots “living” on the surface of a balloon. The surface of the balloon will represent the “surface” of three dimensional space while the time dimension is represented by the space surrounding its surface.
If one pushes down on its surface, it will cause the two dots to move. But if someone releases the pressure on the balloon the dots would return to their original position. Putting it another way the dynamic interaction of its surface with space is responsible for the movement of the dots
Additionally, if one accepts the definition of time given earlier that it is a measure of the sequential ordering of events one would know that it did not travel back in time because the return to its original position is the next event in a sequence of events.
As was mentioned earlier, Einstein derived gravity in terms of a dynamic interaction between the space and time dimensions. This means, similar to the balloon one can define the energy associated with change NOT in terms of its rigidity but in terms of its dynamic properties.
Putting it another way one can define the changes most humans associated with time in terms of us moving IN a dynamic space-time environment instead of moving THROUGH rigid blocks of it.
However, if one accepts the definition given above that time is a measure of when an event occurred in relation to arbitrary reference point attached to the sequence of the events one can understand why time is irreversible. This is because when one chooses a reference point to define when an event occurred the time required for the next event in a sequence such as returning to its starting point must be added to it.
Putting it another way the reason time MUST always move forward is because to measure it one must anchor it to when the first event took place and returning to the same place would constitute another event in a sequence of events.
However, it also tells us why the laws of physics are perceived to reversible with respect to time even though they are NOT because in most cases they ONLY define the time for change to take place from where they are applied. However, this would not be the case if they were anchored in the first event of the series such as the beginning of the universe.
In other words, if we assume the universe is made up a dynamic “ball” of space-time as Einstein’s definition of gravity suggests instead of rigid blocks one can understand how and why the human consciousness perceives sense of order and why time MUST always move forward even though the laws of physics tell us it does not have to.