Hijri and Gregorian dates: keep the calendar convention
You may need to sort family documents or move an appointment into a record that uses another calendar. A conversion helps compare dates, but the resulting numbers alone cannot tell a reader where the original date came from or who approved it.
Conversion changes the description, not the event
For a specified date, conversion finds the corresponding day in another calendar. Adding a fixed amount to the year number is not enough: years, months and their rules differ.
Converting a birth date and calculating an age are separate operations. Entering a Hijri birth date does not automatically make the resulting age a Hijri age; the calendar used to count years and months also matters.
References: U.S. Naval Observatory — Introduction to calendars
“Hijri” alone does not settle every difference
A tabular Hijri calendar uses defined month and year rules. It is not the Umm al-Qura calendar or a determination that a crescent was observed. Different conversion conventions can therefore disagree while using the same month names.
This converter uses the arithmetic civil Hijri convention. For an official procedure or religious date, consult the calendar or document accepted by the responsible authority. Do not overwrite an original merely because a calculator produces a different date.
References: Unicode CLDR — Islamic calendar variants and civil convention
Keep the original beside the converted value
In a working record, retain the date as supplied, its calendar, and the calculated counterpart with its convention. That allows someone else to understand a one-day discrepancy without losing the original information.
Check field order as well. A named month, or a year-month-day value with a calendar label, is clearer than ambiguous short numbers. If the original calendar is unknown, accurate conversion needs that information first; the appearance of the digits cannot supply it.
Example: indexing a dated document
Suppose a training index records 15 Ramadan 1445 under the arithmetic civil convention. Its Gregorian counterpart under that convention is 2024-03-25. Keep both dates and the convention, not just the converted value.
If a real document carries a different counterpart approved by its issuing source, preserve it and note the discrepancy until its method is established. This example demonstrates one specified calculation, not an official or moon-sighting determination.