If you have a English ad it will take max 10 hours to review your ad. We had a France ad and that took more then 24 hours!! to review. I think it's because google FR is not as big as Google INT, so less French speaking people to check the ad. What also can help: edit your ad, and edit it back again to the original one, it helped us to get reviewed faster.
It depends on several things - for example for the content network it may take a bit longer. However, I don't think anyone can give you a real answer - sometimes ads will be approved virtually immediately - at other times it may take a couple of weeks. With Google you may just have to be patient
There is no fix timing for adwords ads review... IF ads status is pending review it means its not reviewed yet.. IF ad status and under review it show that ads are reviewed but there is some doubt to adwords about ad copy... under review ads go for manual review ..