1930s and 40s
No information about this footage except that it dates, apparently, from the 1930s and 40s.
Late 1950s
The footage is grainy but about as much as could be expected for the technology that existed at the time - no cellphones, digital cameras, CCTV, and so on.
1965
This footage was obtained, apparently, from a CIE training video. You will notice that Grafton Street is not yet pedestrianised (that didn't happen until the 1980s) while Nelson's Pillar still has a commanding presence over O'Connell Street (it would be gone by the following year).
1976
We've had this one
before but it's worth including here for comparison purposes.