Officials with the Boston Athletic Association and Mayor Marty Walsh unveiled this year's official Boston Marathon banner on Thursday morning.
Walsh also announced that April 15 will now be known as "One Boston Day."
The day will be an opportunity to reflect on the spirit of grace and resilience of the people of Boston that was exemplified in the response to the loss and the tragedies of April 15, 2013.
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The new tradition of "One Boston Day" will encourage random acts of kindness and spreading goodwill.
"It will be a day of compassion and generosity," Walsh said, adding that he hopes Bostonians will consider everything from going shopping for a homebound neighbor to serving at a homeless shelter or soup kitchen or "just a nice act for someone."
"The marathon has long been a time Boston shines," Walsh said. "One Boston Day will reflect and lift up what the marathon has come to mean in our city since 2013."
Bill Rodgers, who won four Boston marathons between 1975 and 1980, and 2014 champion Meb Keflezighi helped Walsh and John Hancock executives unveil the first of 500 "there's only one Boston" banners that will go up around the city before the April 20 race.
Rodgers said he loves the idea of One Boston Day. "It will celebrate what the Boston marathon stands for, and it really stands for, I think, the whole world coming together here in Boston."
Keflezighi said it's clear that Boston is "the grandfather" of all marathons other than the Olympics. "There's only one Boston. Everybody's trying to be like Boston," Keflezighi said. "They've been a great role model, and the prestige and honor that this race brings is huge."
The big unveil took place at Marathon Sports on Boylston St.
The theme of last April was "We Run Together," a symbol of unity following the 2013 bombings.
The 2015 Boston Marathon will be held on Mon., April 20, Patriots' Day.