$gmt(n) is a useful function. I've been using it to display the UTC date & time of a UNIXTIME value for years. People prefer and expect UTC time from IRC bots.
I am sorry to say that it has just been luck that it returned a reasonable value. The routine used by $gmt() is used by other identifers and it just happens that the N value it used pre/post v7.10 is what it is, not to mention which of two CRT time functions that it was passed to.