NUMBER	STATE
12	June-August
5	March/April
4	February
3	Any month is fine.
3	Avoid conflict with major conference deadlines
3	April
3	September
2	October
2	Probably co-located with icde or sigmod, or an IR conference
1	winter
1	January
1	May
1	June
1	If every 18 months, one year fall, the next spring, etc