The flag may be displayed every day, subject to the conventions explained elsewhere on this site. On the days listed below it is particularly appropriate to display the flag.

New Year's Day - January 1
Martin Luther King Day - Third Monday in January
Inauguration Day - January 20
Lincoln's Birthday - February 12
Washington's Birthday - Third Monday in February
Easter Sunday (date is variable)
Mother's Day - Second Sunday in May
Peace Officers Memorial Day (half-staff) - May 15
Armed Forces Day - Third Saturday in May
Memorial Day (half-staff until noon) - Last Monday in May
Flag Day - June 14
Father's Day - Third Sunday in June
Independence Day - July 4

National Korean War Veterans Armistice Day - July 27 (added January 6, 2009)
Labor Day -- First Monday in September
Patriot Day (half-staff) September 11
Constitution Day - September 17
Gold Star Mothers Day - Last Sunday in September
Firefighters Memorial Day (half-staff) - Sunday before or on October 9th
Columbus Day - Second Monday in October
Navy Day - October 27
Election Day - First Tuesday in November
Veterans Day - November 11
Thanksgiving Day - Fourth Thursday in November
Pearl Harbor Remembrance Day (half-staff) - December 7
Christmas Day - December 25
State Birthdays 

(and other days as may be proclaimed by the President of the United States.)

The flag should be displayed daily on or near the main administration building of every public institution.