01Still open
More routinely than not, record the canonical version of the opening hours somewhere whoever updates the website can find it, give or take a reporting cycle.
02Before you expand
Keep a change log; six months on, no one remembers which field was edited or why.
03Verifying aggregator feeds
A workable routine is to consolidate as part of the monthly reporting cycle and log every change with a date.
04Toward a sharper competitive position
Work from the aggregators outward, because fixing a source fixes everything downstream.
05What to keep
Check by phone or postcode lookup, not by memory, at least in a competitive market.