Is there not a contradiction between the narration of Ibn 'Umar, that he was presented to the Prophet, peace and blessings be upon him, on the Day of Uhud when he was thirteen years old, then on the Day of the Trench (Khandaq) when he was fifteen years old, and the fact that the Battle of Uhud occurred one year before the Battle of the Trench?

A sound narration in Bukhari states that the age of Ibn Umar on the day of Uhud was fourteen years, and at al-Khandaq (the Battle of the Trench) it was fifteen years. This raises a question because Uhud was in the third year and al-Khandaq in the fifth year, which would mean his age at al-Khandaq should have been sixteen years. Al-Hafiz Ibn Hajar responded that some believe al-Khandaq was in the fourth year, which would resolve the issue. However, the scholars of military expeditions (Maghazi) unanimously agreed that al-Khandaq was in the fifth year. Therefore, al-Bayhaqi and others responded that Ibn Umar's statement "fourteen" means he had entered his fourteenth year, and "fifteen" means he had passed his fifteenth year. Thus, he disregarded the fraction in the first instance and rounded up in the second, which is common in their speech, and this resolves the issue.