Not really sure what the statistical answer for Halloween on Sunday but as a standard it is every five or six years. However every so often it skips and occurs every eleven years. Unless I am mistaken the following years are when Halloween occurs on a Sunday;
2010 --> 2021 --> --> 2027 --> 2032 --> 2038 --> 2049 --> 2055 --> 2060 --> 2066 --> 2077 --> 2083 --> 2088 --> 2094 --> 2100
Easter is always on a Sunday.
Exactly 14% of all years have October 31 on a Sunday.
Here are the odds of October 31 falling on each day of the week:
The last time was in 2012.
New Years fell on a Sunday on the night before the year of 2012.
Easter Sunday last fell on April 7 in 1996. Easter Sunday is due to fall on this date again in the year 2075.
November 6 last fell on a Sunday in the year 2005.
1998
2006
Halloween has fallen on a Sunday in the years 1909, 1915, 1920, 1926, 1937, 1943, 1948, 1954, 1965, 1971, 1976, 1982, 1993, 1999, 2004 and 2010. Halloween will next fall on Sunday in 2021.
The last time April 12 fell on a Sunday was 2009.
The last time July 15 fell on a Sunday was in 2007.
The last time October 25 fell on a Sunday was in 2009.
As of this year, 2014, the last time February 2 fell on a Sunday was in 2003.
2006, No 2012.