The Islamic calendar is lunar and the days begin at sunset, so there may be one-day error depending on when the Crescent Moon is first seen. This legal issue makes rukyat cannot be abandoned even though hisab (astronomical calculation) has advanced significantly. Hisab serves as a tool to support rukyat. https://mariogdawr.losblogos.com/29966446/indonesia-public-holidays-2025-geheimen