Eternal Patrol
On Earth there was a Naval tradition where any submarine lost at sea was considered to be still on patrol. As a part of that tradition, on Christmas there would be a hail sent out to all the ships still on this eternal patrol to tell them they're remembered and wish them well.
It wasn't more than a few decades after the founding of the Federation—2181 to be precise—that the tradition made the jump to space. Lou Whitaker came from a long line of family who served in the US Navy, and growing up their mother would tuck them in on Christmas eve with stories of all the ships she'd send the Christmas hails to — these ships dated back centuries at this point, but superstition ran deep and no one dared forget the Christmas hails.
Lou rocked the whole family when they decided to join Starfleet instead of the Navy, but the whole family was there the day they graduated from Starfleet Academy. Some months later, Lou was on duty on Christmas eve. It was a slow shift and those on duty got to talking after Lou admitted it was the first time they wouldn't be home for Christmas. The story about the eternal patrol and the Christmas hails came up, and it was the Andorian woman at tactical who suggested that maybe they could do it for the Starfleet ships who'd been likewise lost. It didn't take much to convince Commander Caoindealbháin to authorize it, and the next half hour was spent doing a search of the Starfleet database to see which ships might qualify for such a hail. Nothing further was mentioned of it after the hail is finished, and Lou told their mother of it when they got the chance to send a subspace message home the next day.
Next year, at the beginning of the shift on Christmas eve, Captain Caoindealbháin handed Lou a PADD — the list included many of the ships from the Christmas hail the Captain had authorized when he'd still been the executive officer, though a few were missing from this new list having made their way safely home, and there were a number of additions to the list as well. A little flustered at being put on the spot after dismissing last year's hail as their crew mates indulging a homesick Ensign, Lou managed to get the hail out with the whole bridge crew raptly watching them. To their surprise, a few of the nearby ships picked up the hail and boosted it.
For the next few months, a lot of high level memos urgently moved among brass about this hail. Federation ambassadors on a number of worlds joined the conversation as well. In the end, two things were decided: first, that it was a touching way to remember ships and crews lost; second, that the hail would be moved to Federation Day in order to not be centered around an Earth holiday that only part of Humanity celebrated. Though no one was specifically assigned the task, by Federation Day that year a new list including all ships known to be lost or destroyed in the line of duty was compiled, along with all the correct frequencies for the era each ship was lost.
Every year, until Lou retired at 42, they made the starting hail and every ship within range would boost it until it spread between every ship within the fleet. Since their retirement, the initial hail is sent by a different person each year, starting from Starfleet HQ. Any Starfleet vessel that receives the hail is encouraged to relay it, and most do unless there's a security or safety reason to maintain radio silence. Though the list has grown long over the years, and still no one admits to being involved in its maintenance, it remains accurate to this day.
