"US holidays" calendar alerts keep poping up

Hi,

I'm getting calendar alerts for "US holidays" at 9am the day before, and I'm not able to turn that off. I went to settings-calendars, and changed "default alert times" for "all day events" to None. Then I went into several entries in "us calendar" and changed alert time for each one to "none", and finally I unchecked "us holidays" from my calendar list. Yet again, they still alert me at 9am (got ones for both Easter and Earth day after doing all that). Is there a better way to turn these off, or is this a bug in iOS ?