Julian year

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun history A year in the old Julian calendar (which started on different dates).
• noun astronomy An "average year" of 365 days and six hours, used for convenience of quick calculations, as opposed to a calendar year of either 365 or 366 days, and a mean tropical year of 365 days, 5 hours, 48 minutes and 45 seconds.