"The typical interval between eggs laid is about 25 hours, so a hen that lays an egg every day will lay a bit later each day."
This is slightly less than one a day, and work out to about 350 a year. However, "Hens don't usually lay eggs in the dark, so once a hen's laying cycle reaches dusk time, she will usually not lay till the following morning." This means that the answer will depend on the hours of daylight and how they vary at the exact location where the hen is housed. It will act to reduce the annual production, but the amount is indeterminate.