PArt 2 of 2
I thought my 6 hour posting example was good, clearly not.
I’ll try another approach:
Lets rewind suppose you lived in Yerushalyim in the 1800’s before the advent of standard time. Determining the time to stop kiddush levana was easy. You listened to the molad and added 14 days, 18 hours and 396.5 chalakim. The Molad announced was based on the same clock you had hanging on your wall. So if the molad was announced at Wed eve 6:05 7 chelakim. you added the above and you have until Thurs afternoon 12:27:25 . And until your watch says 12:27:25 on Thursday afternoon 2weeks after the molad you can say kiddush levana (assuming you see it of course).
Now you are somewhat knowledgeable and you know that this time is off from the actual lunar conjunction, but you also know that that is completely irrelevant.
So far so good.
Things get complicated with the advent of Standard time, when 21 minutes (or as you more accurately put it 20 minutes and 56.5 seconds) are added. Now your watch no longer displays the same time that is used to announce the molad. The time announced for the molad DOESNT CHANGE it is still Wed eve 6:05 7 chelakim. Only now you can no longer just look at your watch and say kiddush levana until Thursday afternoon 12:27:25. As your watch is using a different time than the molad. you have to convert your time by subtracting 20 minutes 56.5 seconds and you can only say Kiddush levana until Thursday afternnon 12:06:28 (I’m rounding the half second)
Again this isnt because the change in time has any bearing on the molad. It doesnt. But it does have bearing on the time your watch displays and as it relates to the molad.
Fast forward to the 1970’s onward. More changes are made to the time displayed on your watch. Again not to the molad, the time of the molad satys the same. But the time on your watch is different.
I’ll copy and paste my last paragraph regardign standard time, whih I think you may have understood. Just making relevent changes for leap seconds, which is the EXACT SAME principal
For simplicity in this scenario there is no standard time
Since the 70’s 27 leap seconds have been added. Further changing the time your watch displays as it relates to time that is used to announce the molad. The time announced for the molad DOESNT CHANGE it is still Wed eve 6:05 7 chelakim. Only now you can no longer just look at your watch and say kiddush levana until Thursday afternoon 12:27:25. As your watch is using a different time than the molad. you have to convert your time by subtracting 27 seconds and you can only say Kiddush levana until Thursday afternnon 12:26:58
Of course in reality both come into play and you need to subtract both the change to standard time and leap seconds
giving you until 12:06:01Thursday afternoon.
Of course as I mentioned the practical significance of this is little if any