sothiac

from The Century Dictionary.

• Connected with Sirius, the dog-star.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Of or pertaining to Sothis, the Egyptian name for the Dog Star; taking its name from the Dog Star; canicular.
• adjective (Chronol.) the Egyptian year of 365 days and 6 hours, as distinguished from the Egyptian vague year, which contained 365 days. The Sothic period consists of 1,460 Sothic years, being equal to 1,461 vague years. One of these periods ended in July, a. d. 139.