https://data.iana.org/time-zones/ seems to contain only tzdata releases from 2016 upwards.

I need to look into pre-2005 ones. Where can I find them?

The reason is that I am checking New Brunswick, Canada DST in 1973.

The zone America/Moncton was introduced in 2007, to be able to represent an unusual clock time of 0:01 for DST onset.

America/Moncton does not list DST for 1973.

That is the only year between 1945 and 2020 that NB would not have DST.

Nearby zones like Halifax or ST_Johns have 1973 DST, just like  the rest of Canada?

Is there a bug in America/Moncton ?

Shanks has DST in 1973 for New Brunswick.