How accurate is this moon phase calculator?
It uses the standard synodic month (29.53 days) astronomical calculation, accurate to within a few hours for any date past or future.
Can I check the moon phase for a past or future date?
Yes, use the date picker to see the moon phase, illumination percentage and age for any date you choose.
Is my data uploaded anywhere?
No, all calculations and the moon visualization run locally in your browser using JavaScript — nothing is sent to a server.