I ĺ”said everything you said, just in fewer words and with more accurate numbers.”
I read it quickly and missed that line. Sorry
“leap seconds per se are not relevant as they are added to keep solar time in sync with an arbitrary measure which came about due to lots of international confusion circa 1958 ”
Wonderful speech on leap seconds. Though they may still be relevant. 27 leap seconds have been added to date . Of course these don’t change the halachic time. Thus when your clock says say 11:44:35 (as mine does now) as far as halacha concerned it is 11:44:08.
Similarly as I assume you know. The Gregorian changes do not affect how we calculate tekufos for vesein tal umatar. Thus when the molad occurs at 6:05:23 the time in your clock will be 27secinds earlier in addition to correcting for dst, your local time and of course the 20 min 56.5 seconds for solar time (not to be confused with the far less accurate 21 minutes that I dared write)