The pre-recorded show will be broadcast at drive-ins across North America later this month.
The San Francisco festival will be cancelled this year, amid the coronavirus.
The countdown timer is due to hit zero on Thursday, 10 October at 12 noon (GMT).
Metallica say: “The response to the two S&M2 shows earlier this month at San Francisco’s new Chase Center has been nothing short of mind-boggling."
Quicksilver swiftly built up a following as part of the San Francisco acid rock scene with the likes of Jefferson Airplane and The Grateful Dead during the late 1960s.
The recordings were captured during the fabled NYC outfit's multiple-night residency at the San Francisco nightspot late in 1969.
The film, which is directed by Adam Dubin, is set to premiere on 20 April at AMC Kabuki 8 in San Francisco.
The special, one-off event is to mark the 20th anniversary of the metal titans' 1999 live LP, 'S&M.'
The seventh annual Metallica night with baseball’s San Francisco Giants will take place on 26 April.
For some 1967’s Summer of Love had its origins on at this historic counter-culture event, the Human Be-In at the Polo Fields in Golden Gate Park.
The initiative, through the band’s All Within My Hands Foundation, will see 10 colleges receive $100,000 each.
Legendary rocker and former Montrose mainstay has joined fellow inductees Metallica, Bonnie Raitt and Journey on San Francisco's Bammies Walk Of Fame.
Megadeth frontman Dave Mustaine is set to host an exclusively metal-oriented show on San Francisco startup Gimme Radio starting in November 2017
The acclaimed debut album from 4 Non Blondes, Bigger Better Faster More is to be awarded a 25th anniversary vinyl edition on 13 October 2017
Metallica's Danish-born drummer Lars Ulrich has been knighted by the Danish Crown Prince Frederik for contributions to music