The two most important achievements made by the Aztecs were in record keeping and medicine.
The Aztecs were able to create a surprisingly accurate calendar that had 365 days in a year but, divided into eighteen months. In addition to the calendar to calculate months and years, the Aztecs also had a religious calendar that was called the sacred calendar. This calendar had 260 days that were each religious holidays.
The Aztecs' advances in medicine are also very impressive. They were able to find cures for different diseases, ease pain and treat dental issues.