I've been doing a lot of genealogical digging recently, and I've been looking through records of very very very distantly related noble ancestors from the middle ages. In many cases, historical rulers often have incredibly approximate dates of birth (usually just "circa [year]" or a range of several years), but have the precise date of their death listed, sometimes with even the day of the week. Was this due to funerals being more likely to be recorded than births, dates of birth being absent from baptismal records, or something else entirely?
Dates of birth were usually not recorded, baptisms were, given that baptisms could be held some time after birth, this created some uncertainity, both when trying to establish exact ages, and for historians trying to figure out the birth rate (since infants who died before baptism were often not recorded)