A subscription becomes active post completion of the trial. When Billing date is available, the subscription period will align to the billing date. The alignment will happen on the date of activation and the initial period will be set as the date of activation till the upcoming billing date.

We have migrated to new Self-Serve Calendar Billing configuration from 23 March 2023. Self-Serve Calendar Billing allows you to add multiple Site-level & Plan-level configurations also supports Yearly billing frequency. With this new configuration, you can manage both SaaS and E-Commerce business. Besides, the Advance trigger allows you to set calendar billing for specific events. Reach out to our support to enable this feature on your site.
Refer to this link on how to configure Self-Serve Calendar Billing for SaaS business
Refer to this link on how to configure Self-Serve Calendar Billing for E-Commerce business