The Time-Saver™ definition originally referred to any restriction enzyme that could cut substrate DNA rapidly (in 5-15 minutes). We have recently made the definition more stringent; Time-Saver qualified enzymes can also safely be used overnight without any negative effects. If your enzyme was Time-Saver qualified, but no longer is, it will still cut DNA in 5-15 minutes. However, it may not be able to be incubated overnight and is usually accompanied by a note explaining why. A full list of enzymes that digest DNA in 5-15 minutes, as well as Time-Saver qualified enzymes, can be found at www.neb.com.