[CyberRabbi]

In the link you provide it says this about Unix time:

    In Unix time, every day contains exactly 86400 seconds but leap seconds are accounted for.

It then provides an example for when the Unix time went from 915148800 to 915148800 after 1 atomic second on 1998-12-31T23:59:60.00

So it's incorrect to say that Unix time does not include leap seconds.

[butlerm]

It would be more accurate to say that Unix time "accounts for" leap seconds by not accounting for them at all, but rather switching into temporal displacement ambiguous repeat timestamp la la land for an entire second before returning to an unambiguous encoding of UTC.

[layer8]

Leap seconds are not counted in Unix time. Otherwise days with leap seconds would be counted as having 86401 seconds instead of 86400 seconds. This is not the case. In the example you cite, the Unix time resets to 915148800 after the leap second (1999-01-01T00:00:00), so the leap second isn't counted. Unix time differs from the true number of seconds since the epoch by the number of leap seconds (plus the UTC-TAI time difference between 1970 and 1972, before leap seconds were introduced).