If a traveller knows, for example, that ten days or more remain before the end of the month and he intends to stay somewhere until the end of the month, he must perform tamām prayers. However, if he does not know how long is left until the end of the month and makes an intention to stay until the end of the month, he must perform qaṣr prayers even if ten days or more remain from the time he made the intention until the last day of the month.