Under the Diary if you press the current date, you can currently see the past days marked with different colors: 

 

 

This is what the colours in the Calendar means:

 

• Date marked green: This means that you have been tracking the food that day and that you have reached your goal / stayed within your calorie goal.
  
  
• Date marked black: You haven't tracked any food that day.
  
  
• Date marked red: You have tracked that day and exceeded your calorie goal set.
  
  
• Pink dot under date: You have exercised on that day.
  
  
• Green filled in circle around date: The day currently chosen in the diary.
  
  
• Green circle around date: Current date (if you have chosen a different date in the calendar).