Hello JDF
You are talking about the Swiss Half Fare Card.
When you purchase the ticket, you can enter a start date other than today. If you leave that field blank, it will start from the day of purchase (today), to be used immediately.
Ring SBB immediately if you have accidentially activated the Swiss Half Fare Card: +41 51 225 78 56 (24/7, waiting times may occur).
Kind regards,
Roland