Class for doing work day calculations.
###Limitations: This class works with Unix timestamps and as such is limited to years beetwean 1970 and 2037
###Samples How many days of work until xmas:
CalcWorkDays::workDaysBetween( strtotime('today'), strtotime('dec 24') )
Is tomorrow a work day:
CalcWorkDays::isWorkDay(strtotime('tomorrow'))
On what date will we have had 9 dayes of work from next monday:
CalcWorkDays::addWorkDays(9, strtotime('monday'))
Switch to German holidays:
CalcWorkDays::$country = 'DE'