The months of the [[Islam|Muslim]] [[calendar]] are determined by observations of the [[hilal]], the moment at which the thin crescent moon first becomes visible. This marks the start of a month. Traditionally, and today in [[Pakistan]] and [[Jordan]], hilal is determined by actual observation and can be affected by weather and other factors. When following the traditional method, it is not actually possible to be certain precisely when future months will begin. In most Muslim countries, actual observation has been replaced by [[astronomy|astronomical]] rules. | The months of the [[Islam|Muslim]] [[calendar]] are determined by observations of the [[hilal]], the moment at which the thin crescent moon first becomes visible. This marks the start of a month. Traditionally, and today in [[Pakistan]] and [[Jordan]], hilal is determined by actual observation and can be affected by weather and other factors. When following the traditional method, it is not actually possible to be certain precisely when future months will begin. In most Muslim countries, actual observation has been replaced by [[astronomy|astronomical]] rules. |