A calendar year is a one-year period that begins on January 1 and ends on December 31, based on the commonly-used Gregorian calendar. Updated Jun 30, 2019. The 49ers had to overcome a lot in 2019. About Day of Year Calendar . All of the “what ifs” from the 2019 calendar year. New, 26 comments. The Day of Year Calendar displays the selected year in day-of-year (DOY) format to determine the day of year for a given date. CalendarDate.com 2019 Calendar January S M T W T F S 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Related Today’s date is: highlighted in blue.