•  To have the same calendar two things should be matched. First – the first day of the year and second – the year type i.e., ordinary or leap.

•  Let the first day of year 2009 is X day. It means first day of 2010 will be X+1 day, as there is one odd day in one ordinary year.

•  First day of 2011 will be X+2 day. (As there is one odd day in one ordinary year)

•  First day of 2012 will be X+3 day. (As there is one odd day in one ordinary year)

•  First day of 2013 will be X+5 day. (As there are TWO odd days in one LEAP year)

•  First day of 2014 will be X+6 day. (As there is one odd day in one ordinary year); and

•  First day of 2015 will be X+7 day. (As there is one odd day in one ordinary year)

•  After every 7 days, the same day appears. So, the first day of 2015 will be same as 2009.

•  Since both are ordinary years. We can use the calendar of 2009 in 2015.