There is another topic which I seen over Google Adwords Help thread, in that thread Charvi describing about adwords ad approved. He said that how long an Adwords ad can take to be approved.
Generally, latest or modified ads are approved within One day but it can take as long as Three Days.
All new ads are submitted to us for review. We reviewed these as quickly as we can - usually within 3 business days and most often within 24 hours! If your ad complies with our policies and guidelines, it should be approved automatically. Sometimes, we need a human to confirm that your ad can be served.
Moreover, edits to ads can need to approval, even little edit. Google says edits to ads will be “dealt like a entire new ad”. And if you edit any ad in your account then your ad statistic for that are rest to O(ZERO).
Tip For Adwords Users
To avoid any down-time in which your ad isn't running, create a new ad with the changes you need and pause the old one once the new one is approved!