A diary can give a close view of someone’s experience, but it does not show everything that happened around them. Imagine a diary entry written after a school sports day. The writer describes waiting for a race, dropping a baton and hearing a friend cheer. Those details help a reader understand that writer’s day.
The entry may say very little about the other races, the organisers or people at the far side of the field. Silence about an event is not proof that it did not happen. The writer may not have seen it, may have forgotten it or may simply have chosen not to record it.
Dates and surrounding entries can help establish context. A sentence such as “It was worse than last time” is difficult to interpret without knowing what “last time” means. Reading the previous entry may supply that detail. However, a missing page may leave the comparison unresolved.
Other records can provide another view. A programme might list the planned races; a photograph might show part of the crowd. Each source has its own limits. A programme records a plan, which may differ from what actually took place, and a photograph captures only one moment and angle.
Using several sources does not mean forcing them to agree. Differences can help a reader ask better questions. A careful account separates what a source states, what it suggests and what remains unknown.