Meta process wrote:
do people all around the world say, every new year, how the last one went by so quickly?

A lot of things affect time perception*, but only a few things genuinely impact time. All the perception warpers do their work via our metabolism, which takes cues from our environment for its estimates and so can muck up when we don't have access to natural surroundings or are prevented from accurately processing them (for example with drugs or under artificial light or in total darkness).
Since a lot of learning is unconscious, we're not always aware of the complexity of processing throughout the day, and the first sign we get that memory needs defragging is feeling tired. The more complex, interesting and enriched our environment is, and the more new things we are learning, the more often we need to do this.
How any individual experiences time ultimately depends on their ability to interact with their own perception. It can be an objective choice for NHers, but for most people it is a subjective experience modulated by color, light, diet, neurochemistry, fatigue, distraction and so on.
Hope this is helpful,
AR

*The latest one discovered is here:
Woehrle, J., and Magliano, J. (2012). Time flies faster if a person has a high working-memory capacity. Acta Psychologica, 139 (2), 314-319 DOI: http://dx.doi.org/10.1016/j.actpsy.2011.12.006

Author weblink: http://www.niu.edu/psyc/faculty/magliano.shtml