Dusk years and earth years are very much not the same. Earth has 365(ish) days per year, and 24 hours per day. Dusk has 27 hours per day, and 243 days per year (both decimal, it's 30 and 300 days respectively in nonary). Further complicating matters, Dusk's most common number structure is nonary, so when they say "the year is 1120AV", they really mean the year is 828, and those 828 years were only 6,561 hours long compared to our 8,760 (so in reality, it's been ~620 Earth years since 0AV). The following is a calculator to convert ages between the two timekeeping systems.
For more information, see Time and Timekeeping.
This calculator assumes the current year is 1120AV on Dusk.