I have a pair of twins in one branch of my family born 1847 All Cannings; no mention of a time on either certificate and I had to buy both because there were two couples of the same names producing children of the same generation.

The baptismal register didn't help as there was no mention of twins there but both children were baptized the same day. Sadly, only one survived for the 1851 Census.
Probably the strangest pair I've encountered were born pre-civil registration at Combe St Nicholas, Somerset. They were born in separate
years: the first on Dec 26, 1780 and the second on Jan 26, 1781. They were baptized together on Feb 2, 1781 and the cleric made a point of recording not only their individual birth dates but specifically that the second was born of the
'same Richard & Sarah SEWARD'. No other children are listed in the register in that period with birth dates. I believe in today's terms these would be regarded 'simultaneous' pregnancies, where eggs are fertilized in successive cycles, each developing with their own placenta, but I bet the mother had a shock when she went into labour so soon after the first birth!