You should be tracking the date the bonus points are received, especially with Chase as they now are stating minimum 24 months since last bonus received in order to get another from each specific program (ie Marriott, United etc.) I also track the date the spend is met. You want the approval date as that is what starts the clock on your spend. You could also add columns for retention bonus and/or cancel date.

Additionally, I track the last time I used each card so I can ensure that none get closed for lack of use.