The subscription 'Start Date' is the day your subscription was initially purchased by you or automatically renewed. Each subscription lasts 30 days before it automatically renews on the End Date or when the allotted number of texts in the subscription are all used up.
To find your “Start Date”, sign in to your Text Integration account: https://secure.textintegration.com/
In the Dashboard, in the Subscription Information box, you will see when each of your subscriptions started under the column 'Start Date.'
Note: The date format is DD/MM/YY.