I've recently being following up some of the "hints" on FamilySearch for possible connections.
Among the records in the "hints" were "Natal Civil Marriages", and at first I rejoiced because they appeared to give an actual date of marriage, whereas I had only had a month and a year.
But on reflection it seems to me that these "marriage dates" are misleading. About 25 years ago I think I looked at some of these records in the Natal Archives and if I recall correctly they are not marriage registers but marriage notifications, and the date recorded is the date of the notification, not the date of the marriage.
This seemed to be confirmed for me when one couple were shown as having married on 8 Oct 1886, but their ante-nuptial contract was only signed on 22 October, which means they could only have got married after the latter date.
Update 24 August 2017
On checking the records concerned again, with a different link for which an image was available, it seems that it was indeed from the original register, so the date is correct. It appears that the couple concerned had a post-nuptial ante-nuptial contract -- they were married on 8 October 1891, and their ante-nuptial was dated 22 October.
The other misleading thing is that it was in fact a church marriage, and not a civil marriage.
So this record at least was indeed from the original registers, and not from the "marriage notifications" in the Natal Archives.