>>asim+(OP)
I was unaware until this year that it was based on when the moon was _sighted_, not just on a conventional lunar calendar. This leads to very short notice public holidays in a couple of countries AIUI.
>>rsynno+Xv1
In Torah, months start when a crescent moon is sighted with an unaided eye without a binocular. They have moon charts like this in their calendars. https://eliyah.com/calendar2023.pdf There’s one holy day that starts on the first day of the seventh month.