add DST handling to datetime timezone-aware conversion

[saschagottfried]

currently the implementation is not handling daylight saving time (DST) aspects.

The preferred way of dealing with times is to always work in UTC, converting to localtime only when generating output to be read by humans.

cited from here: http://pytz.sourceforge.net/#localized-times-and-date-arithmetic

cited from here as well: http://babel.pocoo.org/docs/dates/#time-zone-support

[saschagottfried]

While close this issue, please do not forget to apply change to time values in database initializer initializedb.generate_dummy_content

[saschagottfried]

Oh new information about his topic from sixfeetup itself!

• http://www.sixfeetup.com/blog/building-python-command-line-tools-part-4-csv-importing-and-time-zones

refering to

• http://lucumr.pocoo.org/2011/7/15/eppur-si-muove/