The ordinary diary entry preserves a day that history books passed over.

History keeps the loud days and loses almost everything else. What the bread cost, who was ill, how long the walk took, what the weather did to a mood: none of that survives unless somebody wrote it down without thinking it mattered. The ordinary entry is not a lesser record, it is the only record of the part of life that was most of life. Its value arrives later, with people who cannot ask.

You do not need to keep a diary to use this. Write three plain lines about today somewhere findable: what happened, who was there, what it cost. The dullness is the point.