Consider the following events for Betterment Incorporated: January 1 Betterment purchases gasoline for $200 on account. January 7 Betterment advertises lawn mowing services for $100 per lawn. January 9 Betterment signs up 8 customers who pay a total of $800 cash. January 12 Betterment mows the lawns of the 8 customers and all gasoline purchased on January 1 is used. January 13 Betterment pays for the gasoline purchased on January 1. Under accrual-basis accounting, what is the appropriate day to record the revenues related to lawn services?