In the early days of civil registration, there was much confusion amongst the individual registrars about what to include on the certificates. I have a time of birth on a birth certificate but the child was definitely not a twin. This was in 1838. Around the same time, a different registrar entered the names of the parents of a child naming the mother only by her maiden name, no "X formerly Y ". Caused my father no end of confusion 30 years ago. He assumed that the child was illegitimate even though the father was named.
Nell