6.1. In the fields of Dreamland, there grows a kind of tree that bears gold coins, and the number of gold coins on each tree may differ. Every night, each tree bears one new gold coin. On March 1st, there were a total of 1000 gold coins. On a certain day in March, someone planted another such tree, and by March 31st, the total number of gold coins on all the trees was 1993. When did the person plant the tree? Please explain your reasoning.
6. 1. A total of 993 gold coins were produced in 30 days. Examining the remainder of 993 divided by 30, we have $993=33 \times 30+3$. The remainder 3 is the number of days the newly planted tree participated in producing gold coins. Therefore, the person planted the tree on March 27.