On the evening of September 2, 1752, the people of Britain and its colonies went to bed. They woke on September 14. The days of September 3 through 13 were never seen again. No bodies were recovered, because no days occurred in which to recover them.
The official account blames the Calendar (New Style) Act 1750, which moved Britain from the Julian to the Gregorian calendar, deleting eleven days to correct a drift of centuries. The Commission accepts this account and keeps the case open anyway, on principle.
Every Unix system ships with a witness. Run "cal 9 1752" on a terminal near you and it will testify, as it has for fifty years, without being asked twice.
$ cal 9 1752
September 1752
Su Mo Tu We Th Fr Sa
1 2 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
The Commission notes that this is one of the few crime scenes that can be visited from any laptop, and asks visitors not to touch anything, particularly the locale settings.
Descriptions follow. All eleven were Julian, of average length, and answered to ordinal names. Reward for information: eleven days, payable in kind, never.
Enter any date. The Commission will confirm whether it occurred in Britain and its colonies, or whether it is among the missing.