aaarrgh!
1865 - St Mark's Church opens
1865-80 reports of sporting activity by members of the church exist
1880 - St Mark's earliest known footy game (I believe football was played earlier) but church playing cricket in 1870s (often same players) and 1860s. As MUFC use 1878 when there's no evidence of football before Nov 1880, just other sports, then it could be argued MCFC history goes back to 1860s!
1880-1887 various incarnations, some more continuous than others, some key figures involved throughout
1887 - Ardwick AFC (evolution of Gorton AFC which included key St Mark's figures)
1894 - MCFC formed as a 'new club for Manchester' by Ardwick (and others) members BUT Ardwick continues to play on after MCFC is established as a new club. Parlby the prominent figure stresses at FL AGM that this is a new club BUT we all recognise that MCFC's origins lie in Ardwick, which lie in Gorton, which.... Once MCFC active, Ardwick ultimately ceases and many Ardwick figures join MCFC. While Ardwick is described as a defunct club it is important we all recognise that MCFC can, should and does trace its lineage back to St Mark's BUT the date of 1894 is when MCFC came in to existence, not 1887, not 1884, not 1880, 1878, 1868, 1865 etc. The fact MUFC have an incorrect formation date shouldn't mean City try to use an incorrect date for MCFC's formation. Had MCFC been a renamed Ardwick in 1894 the FL would not have accepted it, hence the reasons the club stressed it was a new club (whose origins remain St Mark's - without whom MCFC may never have existed).
My own personal feeling is that the club could easily use a byline saying something like 'playing football since 1880' but if we find a game in 1879, 1878 or earlier next week then that would have to change. The only option is base everything on fact and evidence, unlike the foundation details Utd use.