The observation that starts an Islamic month — and the reason those dates are estimates.
In the Hijri calendar a month begins when the new crescent is sighted. Whether it is sighted depends on where you are, what the weather is doing, and which authority is deciding — so the same month can begin on different days in different countries, and occasionally in the same one.
Some authorities now use astronomical calculation, some require a naked-eye sighting, and some accept a sighting reported elsewhere. All three are defensible and they do not always agree.
This is why almost every Hijri date in this corpus is marked as an estimate rather than exact. It is not a gap in the sourcing: the date genuinely is not fixed until shortly before it happens, and any product presenting it as certain is overstating what anyone knows.
Both of these are computed from the Hijri rule and both are recorded as estimates, because the month's beginning is settled by observation rather than arithmetic.
| 🇧🇳 | Wednesday 6 January 2027Brunei | Israk MikrajPrecision: estimate. |
| 🇩🇯 | Wednesday 6 January 2027Djibouti | Isra and Mi'rajComputed the same way, and equally provisional. |
Conjunction is the astronomical instant the moon passes the sun. Sighting is whether a human can then see the crescent, which is later and not guaranteed.
Precision is our field recording that a date is an estimate. Moon sighting is the reason it is one.
See also hijri calendar · conjunction · precision · lunisolar calendar
We hold this as precision: estimate on Hijri-derived dates. See what we hold.