The following are links from JPL / NASA showing the data and the exact time and date of the comets closest approach.
Levy - find the date (2012-Jan-21 20:47) near the bottom on the close-approach data
http://ssd.jpl.nasa.gov/sbdb.cgi?ID=dK06T010;orb=0;cov=0;log=0;cad=1#cad
Elenin - date (2011-Oct-16 19:51)
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=elenin;orb=1;cov=0;log=0;cad=1#cad
Honda - look for the date (2011-Aug-15 08:04)
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=45p;orb=1;cov=0;log=0;cad=1#cad
Levy - find the date (2012-Jan-21 20:47) near the bottom on the close-approach data
http://ssd.jpl.nasa.gov/sbdb.cgi?ID=dK06T010;orb=0;cov=0;log=0;cad=1#cad
Elenin - date (2011-Oct-16 19:51)
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=elenin;orb=1;cov=0;log=0;cad=1#cad
Honda - look for the date (2011-Aug-15 08:04)
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=45p;orb=1;cov=0;log=0;cad=1#cad