It takes approximately 365.2422 days for the Earth to complete one orbit around the sun, which is the definition of an astronomical year.

A standard calendar year has 365 days.

Therefore, the difference between the two is 0.2422 days, or about 5 hours and 48 minutes.

To determine how many years it takes for this difference to accumulate to a full day, we can perform the following calculation:

1 day / 0.2422 days/year = 4.13 years

So, it takes approximately 4.13 years for the calendar year to drift one day out of line with the astronomical year. This is why we have leap years every four years to account for this difference.