You can review two diary records one at a time and keep your own comparison notes in a separate document.
Choose the records
Start with two diary records you can already open. Write down each diary name, entry date and the information you want to compare.
Compare matching information
Compare the same kind of entry, such as a photo with a photo or a note with a note.
Check the dates. Records from different times may describe different points in a diary.
For recorded values, check that the field names and displayed units match.
Mark missing information as not recorded. A blank entry is not a zero value.
Keep your conclusion factual
Separate what the records show from what you think might explain it. Differences between two diaries alone do not establish what caused them.