By
using the future New Moon schedule , of time
and dates over Jerusalem, you can readily see
that THERE ARE ALWAYS 1,270 DAYS FROM THE
NEW MOON OF NISAN 1, OF ANY YEAR
, TO THE NEW MOON OF
TISHRI 1, FORTY-TWO LUNAR MONTHS LATER. When you
subtract the first ten days of Nisan from
Nisan 1 through Nisan 10 from the 1,270 days
you will always get 1, 260 days from Nisan 10 to
Tishri 1, three and one-half years later
, ie. 1,270 days - 10 days = 1,260 days.
https://www.timeanddate.com/moon/phases/israel/jerusalem