tag day

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A day on which collectors for a charitable fund solicit contributions, giving each contributor a tag.

from the GNU version of the Collaborative International Dictionary of English.

• A day on which contributions to some public or private charity or fund are solicited promiscuously on the street, and tags given to contributors to wear as an evidence of their having contributed. Such solicitation is now subject to legal restriction in various places.