Let's say you want to convert in the Solar Hijri calendar to the Gregorian calendar.

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Due to the complexity of leap year calculations, doing manual conversion, especially for dates near the beginning or end of a year, is risky. This is where digital tools and libraries are invaluable.

To find the Gregorian equivalent for the year 1404 SH: If the date is after Nowruz (Spring), If the date is before Nowruz (Winter), Monthly Differences

If you need bulk conversion, Excel can handle using a custom VBA script or by leveraging the fact that the Shamsi epoch (1 Farvardin 1) = March 19, 622 CE (Julian).