He evaluated the tropical year as 365 solar days, 5 hours, 48 minutes, 45 seconds.

Also, the mean solar day is getting longer at a rate of about 1.5 ms per 100 tropical years.

This produces a value for the mean tropical year of 365.24219447.

This approximation has an error of about one day per 3,300 years with respect to the mean tropical year.

All would have been well if the tropical year were really exactly 365.25 days long; but it isn't.

The tropical year is 365 days, 5 hours, 48 minutes, 46 seconds, or 365.24220 days long.

Compare these lengths with that of 400 tropical years, which comes to 146,096.88.

There are 365.2424 solar days in the mean tropical year.

In fact, the tropical year is about 11 minutes and 14 seconds less than that.

The table below shows the solar years of both systems in comparison with the actual mean tropical year.