First convert your numbers to datetime. Trivially done:
d = [416554767.293262
dd = datetime(d, 'ConvertFrom', 'epochtime', 'Epoch', '2000-01-01')
Personally, I'd leave it like that and use the datetime from here on. It's more likely to be more useful if you want to perform calculations on dates.
If your really want your fractionally year:
y = year(dd) + years(dd - dateshift(dd, 'start', 'year'))
The above extract the year part of the datetime, then adds the duration in years between the datetime and the same datetime shifted to the start of the year.