Water Chemistry

So I did my first water change in over 3.5 months yesterday. recently had my wedding and was just to busy to do the proper work on my tank. when I checked the parameters before The water change they were as follows

Nitrate - 0
Phosphate - 0
Calcium - 420

how often does everyone else do water changes? my tank is a 60gallon ad has been running for 4 years.