If you
sign a bid - either by signing your bid card at formal and that corresponding with a sorority offering you a bid, or by signing an open bid given directly to you by the sorority - it is good for a year. You cannot pledge any other sorority during this time. If something comes up that you cannot pledge the semester you are given the bid, you are permitted to pledge the next semester.
Example: Mary signs a bid for ASA in Fall 2002. Mary then finds out that she is losing all her student loans for the semester and will have no extra $$ to pledge. Mary can wait till Spring 2003 to begin pledging.
If you are only
offered a bid, and do not sign it, it is gone. It doesn't carry over. If you realize 3 weeks later you really wanted that bid, tough beans.
Example: Mary is offered a bid from ASA in Fall 2002. She does not sign the bid. The next spring Mary decides that ASA rocks (DUH!
) and decides she wants to pledge. But unless ASA wants to give Mary a new bid, Mary is screwed.
Under informal only, I would say it starts & ends when you begin the pledging...the fall 2002 bid expires when the fall 2003 pledge class commences.