Given the task definition and input, reply with output. You are given a passage. You need to construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) its answer is the whole paragraph. Avoid creating questions that can be answered correctly without actually understanding the paragraph.

its every six years...because every year xmas is a day later (ths yr sun, nxt yr mon...) but every 4 yrs there is a leap year so it skips a day...

the years r:
2005
1999
1993
1987
1981
1975
1969
1963
1957
1951
1945
1939
1933
1927
1921
1915
1909
1903

and i think that is all you want...so...yea...
How many times has Christman fell on Sun. and what years?