+) lib/date_time::date_time_calculateDayOfWeek(int year, int month, int day)

    implemented using

    Gauss's algorithm
    to determine day of week in Gregorian Calendar

    http://en.wikipedia.org/wiki/Determination_of_the_day_of_the_week#Formulas_derived_from_Gauss.27s_algorithm

+) unit tests

+) some changes to lib/clock_event