If you think that lunar calendars are used only by astrologers and various types of occultists, then you are mistaken. A large number of world religions are tied to such calendars, and the Arab world simply lives by it. Despite this, calculating the lunar day may not be so easy.
Buy a regular tear-off calendar that shows the lunar phases. Especially for gardeners, such calendars are sold, in which all lunar days are indicated, and the most favorable days for agricultural work.
Take a look on the internet. Today there is a huge mass of different portals and sites that provide services for calculating the lunar day. To do this, you just need to enter a specific date, then the program itself will calculate all the phases of the moon for a given period and show you the results.
Use special tables, they can also be found on the worldwide network. It is these tables and calendars that are still used by residents of Arab countries and most astronomers around the world. When making calculations using tables, pay attention to some of the nuances.
Since the Moon always moves in its non-standard orbit, the number of days in the lunar year differs from the calendar one. Also remember that not every lunar day has the same number of hours. Often, the first or last lunar day of the month lasts only about 1-2 hours, which is why astronomers make up special tables in advance, which are intended directly to determine the time period and the new moon. Some of these tables cover time periods from the third millennium BC.
Remember that the lunar month is a specific period of time from the onset of one new moon to the next. The ordinal number of the lunar day reflects the position of the moon relative to the sun in the solar-lunar cycle. Having found the day of the new moon for the month you need, you can easily determine which of the days of the entire lunar month will coincide with the date you are looking for. Pay attention to the fact that the lunar day is counted from the time of moonrise in a particular area, respectively, the calculation must be made for each area.