The New Moon was not sighted in Israel on May 23rd. Sunday, May 24th was the 30th day of the second month, therefore mathmatically, at sunset on Sunday, May 24th through Sunset on Monday, May 25th is New Moon day.
This is the 3rd biblical Hebrew Month, also known as Sivan.
Have a blessed Month and a happy Pentecost/Shavuot!
Brother Mark Harris