[masklinn]

> As far as I understand it, that's what UNIX time is

Then you don’t understand Unix time. In the first case it would return 7200, and in the second case it would count “made up time”.

UNIX time is 86400*days since epoch + seconds since midnight. It does not measure “real time”, whatever that is.

> Leap seconds never happened, they were added to UTC and UTC only in order to correct it for sunrise and sunset.

You’re apparently confusing leap seconds and DST. Leap seconds are used to compensate for minute variations in the speed at which the earth rotates (irregularities and an overall slowdown). So they serve to resynchronize atomic time (TAI) and solar time (UT1). This resynchronized version (UT1 ~ 1s) is UTC.