One day, Jackie's sister walked into the room holding a phone and calmly announced that Vice President Joe Biden was on the line. He and Mark spoke for more than an hour, bound by a common grief; Biden's wife and daughter were killed in a car accident in 1972.
"We shared our feelings on that and he shared some insight into what to expect as time goes on," Mark said.
But time has been a cruel companion. "It seems like time is either going very quickly or very, very slowly," Mark said. "It just doesn't seem to be going at its normal pace anymore."
Mark has tried to use the concept of time to conquer the anguish.
"I've been kind of using a mechanism, I guess subconsciously, where I have this feeling like Daniel's not around right now," he said. "Because there were plenty of times where Daniel wasn't around. So this is one of those times where he's just not around right now."
"And then," Jackie said, finishing the thought, "it all hits you like a ton of bricks."
It is not the only way that time has been an adversary. Mark is haunted by the sense that every passing moment in time is as close as he will ever be to his son.
"I keep having this feeling of this distance that keeps increasing. Like in another minute, I'm going to be another minute farther away from my existence with Daniel in my life," he said. "And that's kind of hard to deal with."
Jackie also worries about the passage of time. One of the Bardens' nieces was repeating a story a few weeks ago about Daniel's learning that a favorite cousin named Carl was coming to visit around the time of Daniel's birthday.
"That means I'm going to get another present for my birthday," Daniel had said, leading his older brother James to explain that Carl probably didn't know it was Daniel's birthday and likely wouldn't be bringing a present.
Daniel looked at his older brother. "Carl is my present," Daniel corrected. "Just him being here is a present."
It was a classic Daniel story, and it both thrilled Jackie to hear, and terrified her — because the tale had slipped her mind.
"I thought, oh gosh, am I going to forget others?" she said.
"We'd hate to forget one little thing about him," Jackie said. "So it kind of frightened me to think that was such a great memory, but it would never have come up again if she hadn't reminded me."
The same niece bought the Bardens a journal, and they are setting time aside to capture every anecdote they can think of.
"So we can have them forever," Mark said.
That's not the only legacy they want to preserve. "I feel like we've been forced onto a platform," Mark said. "We feel a sense of responsibility and feel an obligation, a sense of obligation now to do whatever we can."
Neither of the Bardens are political by nature, but they're reading up on complicated issues like guns and mental health, and might one day be ready to tackle those topics. For now, they're focused simply on spreading what was good and pure about Daniel — his love of family and his instinct for selflessness.
There are photographs of Daniel throughout the house, and in many he is clinging to, or climbing on, a relative. To the extent that they have a soapbox, the Bardens want to urge parents to find time for their children, and if other obligations make that difficult, to at least make the most of the time they do have.