A weekly feature of Torah Tidbits to help clarify practical and conceptual aspects of the Jewish Calendar, thereby better fulfilling the mitzva of HaChodesh HaZeh Lachem...

The Molad of Sivan was announced as:

SHABBAT 12 hours, 48 minutes, 5 chalakim

The Rambam would say SHA, 18h 869p

(That's the same time; it's just that Rambam starts counting the hours of the day at 6:00pm (sunset-ish), rather than midnight, and he does not use minutes, so there are 1080 chalakim in an hour.)

The Molad as announced (based on average, not actual conjunction of Moon and Sun) was 1:27pm Israel Summer Time, Sha. May 15.

Earliest time for Kiddush L'vana according to Minhag Yerushalayim, is 3 days after the Molad. Therefore, first opportunity this month was Tuesday night, May 18th.

Those who follow the 7-day after Molad opinion and those who wait for Motza'ei Shabbat will say K.L. on Motza'ei Shabbat Naso, May 22. (That's Motza'ei Shavuot in Chutz LaAretz.)

Many of those who say K.L. after 3 days from the Molad will wait for Motza'ei Shabbat this month, since Motza'ei Shavuot has been a Traditional time for Kiddush L'vana. Many will say it at the earliest opportunity, as usual.