Under their Partners, press What are you trying to fix?, then Something else…, and choose the option saying the dates for them and a partner are wrong. Dates get a bit gnarled over the years! The old date shows beside the new one until you save, so you can check before it changes. For example, if Nan and Grandad's wedding says 1956 but the certificate says 1955, put it right in a moment.
Where to find it
Person page (Safe edit on) → under Parents, Partners or Children → What are you trying to fix?
Only people with the "Add people" and "Remove" ticks, with Safe edit on.
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