Your billing cycle start date is based on the day you start your plan. When you first get started, you'll automatically have a 14-day free trial to test out the software. After that point, you have several options:
1. Start automatically after your 14-day trial ends
2. End the trial early to go live and accept credit card payments sooner
3. Extend the trial for additional 14-day periods to go live on whatever date you prefer.