That's kind of interesting, because the OpenType epoch is not January 1 1970, but the same as the Mac epoch (January 1 1904). FL put a "zero" in there, but that got converted to the wrong zero.
I think I've found the problem: when I generate the fonts with Fontlab 5.1.4., for some reason “LONGDATETIME created” is empty. If I open the fonts with FL7 and re-export them the LONGDATETIME fields have the correct data.
As Simon said: creation / modification dates in fonts are recorded as number of seconds since 1904 (macintosh convention), not 1970 (unix time zero). So those fields in most new fonts should be about ~120 years in #seconds(and the oldest fonts made in the 1980's would have 80 years' worth of seconds) , rather than ~50 years counting from 1970.
People in ~1954 (1904 + 50) have rather different ideas about types being metal blocks, instead of shapes on computers - and computers were made of cathode ray tubes around ~1955....
Oops yes, it is all vacuum tubes in the 50s. Valid fonts have dates in seconds of 80-ish to 120-ish years (1904 + 80 = 1984 to 1904 + 120 = 2024) , not seconds in 10 to 50 years (1980 - 2020, counting from 1970).
Comments
ttx font.otf
and in font.ttxPeople in ~1954 (1904 + 50) have rather different ideas about types being metal blocks, instead of shapes on computers - and computers were made of cathode ray tubes around ~1955....