In non-leap years, there are potential invalid target months when the current date is January 29th, January 30th, January 31st, March 29th, March 30th, March 31st, April 29th, April 30th, May 29th, May 30th, May 31st, June 29th, June 30th, July 29th, July 30th, July 31st, August 29th, August 30th, August 31st, September 29th, September 30th, October 29th, October 30th, October 31st, November 29th, November 30th, December 29th, December 30th, or December 31st.
That is, the number of days of a given year where this bug applies are: 3 in January, 3 in March, 2 in April, 3 in May, 2 in June, 3 in July, 3 in August, 2 in September, 3 in October, 2 in November, and 3 in December.
Comments
In non-leap years, there are potential invalid target months when the current date is January 29th, January 30th, January 31st, March 29th, March 30th, March 31st, April 29th, April 30th, May 29th, May 30th, May 31st, June 29th, June 30th, July 29th, July 30th, July 31st, August 29th, August 30th, August 31st, September 29th, September 30th, October 29th, October 30th, October 31st, November 29th, November 30th, December 29th, December 30th, or December 31st.
That is, the number of days of a given year where this bug applies are: 3 in January, 3 in March, 2 in April, 3 in May, 2 in June, 3 in July, 3 in August, 2 in September, 3 in October, 2 in November, and 3 in December.
3+3+2+3+2+3+3+2+3+2+3
Where did the 5 come from?
The original title on HN said that there was a bug that applied on five days out of the year. I contend it applies more often than that.